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Old 2021-11-25, 23:59   #12
MattcAnderson
 
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"Matthew Anderson"
Dec 2010
Oregon, USA

3×17×23 Posts
Default Four OEIS.org sequences

Some OEIS.org sequences
I think these are cool.

The positive integers
1,2,3,4,5,6, ...
A000027

Odd numbers starting with -1
a(n) = 2*n - 1 with n = 0,1,2,3, ...
-1,1,3,5,7,9, ...
A060747

Product of decimal digits of n
0,1,2,3,4,5,6,7,8,9,0,1,2
A007954

Hours struck by a clock
1,2,3,4,5,6,7,8,9,10,11,12, 1,2,3, ...
A034326

Enjoy.
Matt
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Old 2022-06-14, 15:37   #13
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"Matthew Anderson"
Dec 2010
Oregon, USA

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Smile Good primes in OEIS

Yesterday, I learned what a 'good prime' number is.
See Wolfram.com website
https://mathworld.wolfram.com/GoodPrime.html


oeis.org/A046869

Title
Good primes (version 1):
prime(n)^2 > prime(n-1)*prime(n+1).
5, 11, 17, 29, 37, 41, 53, 59, 67, 71, 79, 97, 101, 107, 127, 137, 149

oeis.org/A028388
Title
Good primes (version 2):
prime(n) such that prime(n)^2 > prime(n-i)*prime(n+i) for all 1 <= i <= n-1.
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Old 2022-06-21, 05:59   #14
MattcAnderson
 
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"Matthew Anderson"
Dec 2010
Oregon, USA

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Unhappy Matt vs OEIS.org editors again

HI Mersenneforum and others,

I have 3 sequences that I want to make comments on. I'm not getting my way in my oeis.org account.

Maybe a reader here also has authority at oeis.org
see from my account

Drafts by Matt C. Anderson
(In many browsers, middle-clicking on any of the links below will open it in a new tab.)

Showing all changes.
Sequence Status First Edited Last Active Draft by Reviewed or edited by
A023203 editing +3 −2 Jun 18 05:03 Jun 19 01:41 Matt C. Anderson (3/3) not yet proposed for review
A153419 proposed +4 −3 Jun 18 04:53 Jun 21 01:49 Matt C. Anderson (3/3)
A272176 proposed +8 −1 May 25 13:27 Jun 21 01:45 Matt C. Anderson (3/3)

I'm tired of wrastling with this for tonight.

I feel oeis should be a robust data base with lots of interesting facts about numbers and prime numbers in particulat. But that is just my two cents worth.

Does anyone know whtat the 'score' numbers are under status?

Good night,
Matt
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Old 2022-07-10, 01:12   #15
MattcAnderson
 
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"Matthew Anderson"
Dec 2010
Oregon, USA

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Smile the oeis.org is interesting

A look

A52 is also an excelent one. It involves alphabetical order.
https://oeis.org/A000052
Cheers
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Last fiddled with by MattcAnderson on 2022-07-10 at 01:33 Reason: edited to add
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Old 2022-07-10, 01:42   #16
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"Matthew Anderson"
Dec 2010
Oregon, USA

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Thumbs up

check it out
https://oeis.org/A000062
This one involves a Beatty sequence Betty :--(


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A000064 Partial sums of (unordered) ways of making change for n cents using coins of 1, 2, 5, 10 cents.
(Formerly M1002 N0375)
https://oeis.org/A000064

Again ... Number of unlabeled rooted trees
https://oeis.org/A000081

another interesting sequence oeis.org/A15
Smallest prime power >= n.
to wit -
A15 1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, 13, 13, 16, 16, 16, 17, 19, 19
n __ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

If you are familiar with mathematical group theory, see oeis.org/A19
The number of permutation groups is like the number of reorderings of a numbered set. Take the counting numbers 1 to n. Then consider the number of ways to move the numbers around. Volla! you have A19.
Cheers

Last fiddled with by MattcAnderson on 2022-07-17 at 22:38 Reason: added A15
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