Forum: enzocreti
2020-10-27, 13:01
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Replies: 10
Views: 880
a difficult problem
Let be N a nonnegative integer.
I search integers N such that
N+20=s^2*p and N+19=q^2*(2*p+1), where s and q are integers>1 and p is a prime>2 and (2p+1) is a prime as well.
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Forum: enzocreti
2020-09-30, 13:44
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Replies: 2
Views: 841
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Forum: enzocreti
2020-09-29, 14:46
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Replies: 1
Views: 483
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Forum: enzocreti
2020-09-29, 09:26
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Replies: 3
Views: 589
sigma(n)=x*(x+1)^3
let be sigma(n) the sum of the divisors of n
something is known about numbers n such that
sigma(n)=x*(x+1)^3 with x positive integer?
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Forum: enzocreti
2020-09-01, 08:43
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Replies: 3
Views: 1,408
...factorial(n) plus/minus 1 is semiprime
Is there an Oeis sequence dedicated to numbers n such that n!+1 and n!-1 are both semiprime? An example is 20970
Infact 20970!+1 is semiprime and also 20970!-1 is semi prime
No the...
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Forum: enzocreti
2020-09-01, 07:53
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Replies: 20
Views: 1,919
...i did not...
i did not take into account that N must be 10^m mod 41
let's guess congruent to 1 mod 41
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Forum: enzocreti
2020-09-01, 07:32
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Replies: 20
Views: 1,919
...not that's not prp
how about this:
(2^1430136-1)*10^430514+2^1430135-1???
I made a stupid mistacke
the candidates have the form
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Forum: enzocreti
2020-09-01, 07:21
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Replies: 20
Views: 1,919
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Forum: enzocreti
2020-08-31, 15:43
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Replies: 20
Views: 1,919
Pg(69660) is prime
69660 is multiple of...
Pg(69660) is prime
69660 is multiple of 215 and congruent to 215 mod 323...it is also 6 mod 13... using wolphram numbers of this form are 69660+xn where x i don't remember what it is.
69660...
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Forum: enzocreti
2020-08-31, 13:52
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Replies: 20
Views: 1,919
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Forum: enzocreti
2020-08-31, 11:27
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Replies: 20
Views: 1,919
probable dud
((2^1875230-1)*10^564501+2^1875229-1) has small factors?
I don't know...:smile:
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Forum: enzocreti
2020-08-29, 08:01
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Replies: 11
Views: 2,133
... 56238...
56238 is a not palindromic number such that the reverse 83265 (squarefree) also belongs to Oeis sequence A165256. Are there other examples of not palindromic numbers belonging to A165256 whose...
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Forum: enzocreti
2020-08-28, 18:02
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Replies: 11
Views: 2,133
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Forum: enzocreti
2020-08-28, 16:42
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Replies: 11
Views: 2,133
... 75894...
Pg(56238) is prime and also pg(75894) is prime
56238 and 75894 are multiple of 546.
56238 and 75894 are square free and belong to the Oeis sequence you mentioned
Pg(n) is the concatenation...
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Forum: enzocreti
2020-08-28, 14:46
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Replies: 11
Views: 2,133
numbers of yet another particular type
Consider numbers N squarefree that is in the factorisation of N there is no prime facor raised to a power greater than 1.
56238 is square free
56238 has five digits
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Forum: enzocreti
2020-08-27, 07:50
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Replies: 0
Views: 932
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Forum: enzocreti
2020-08-19, 05:48
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Replies: 8
Views: 4,527
Q77I
215 69660 92020 541456 are...
Q77I
215 69660 92020 541456 are congruent to plus or minus (6^k-1) mod 323 for k=3,2
69660=(2^5*3^7)-(2^3*3^4) so it is the difference of two 3 smooth numbers (2^a*3^b)-(2^(a-3)*3^(b-3))
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Forum: enzocreti
2020-07-23, 07:33
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Replies: 0
Views: 1,413
pg(308899)
pg(69660) is prime
pg(92020) is prime and 92020+239239 is prime
pg(92020+239239) is prime
Now i consider
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Forum: enzocreti
2020-07-02, 09:29
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Replies: 0
Views: 1,270
collatz 3x+1
I found a forumula about the 3x+1 problem
let be T(k,n) the trajectory starting from integer n.
k is the number of iterations
T(0,n)=n i think
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Forum: enzocreti
2020-06-21, 22:01
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Replies: 4
Views: 2,212
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Forum: enzocreti
2020-06-20, 17:55
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Replies: 4
Views: 2,212
Pg(6231) and pg(51456)
There are two primes pg(6231) and pg(51456) with 6231 and 51456 multiple of 201
51456(even)=201*(2^8)
6231(odd)=201*(2^5-1)
Pg(541456) is probab prime
541456=(46^2-1)*2^8+2^4
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Forum: enzocreti
2020-06-19, 21:12
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Replies: 0
Views: 1,221
Lcm(344,559) 331 and pg primes
Pg(215), pg(69660),pg(92020) pg(541456) are prp with 215, 69660, 92020 and 541456 multiple of 43.
215, 69660, 92020, 541456 are plus/minus 344 mod 559
lcm(344,559)=4472
4472=8*331+456*4
...
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Forum: enzocreti
2020-06-18, 19:26
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Replies: 4
Views: 2,212
Pg(92020) and pg(331259)
Pg(92020) and pg(331259) are probable primes
331259=92020+239239
92020 and 331259 are congruent to 5 mod ((331+456*6)*6+1) where 3067=331+456*6 is a prime
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Forum: enzocreti
2020-06-17, 10:45
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Replies: 4
Views: 2,212
Pg(92020) pg(69660) and pg(541456)
Pg(92020) pg(69660) and pg(541456) are primes
92020 541456 69660 are 10^m mod 41 and multiple of 43
541456 is multiple of 787
92020 and 69660 are congruent to 10^s mod (787+456*r) for some...
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Forum: enzocreti
2020-06-15, 10:24
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Replies: 4
Views: 2,212
Pg(75894) and pg(56238) and other random pg(x)
Pg(75894) and pg(56238) are primes or at least probable primes
I noticed that 75894 and 56248 are multiple of 546 and congruent to 24 mod 54
Using Wolphram (Chinese remainder theorem) I was...
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