This one isn't in the OEIS

R2357 · 2020-10-31, 07:12

Hello,

New puzzle that I thought up :

What sequence's representation starts with 5, 16, 361.

It's not in the online encyclopedic integer sequences, so you will have to think a bit, then again, it's not quite challenging :)

TrojH · 2021-01-12, 23:14

Hello. Newbie here.

Looks pretty easy to me:

(5-1)^2=16
(5+16-2)^2=361
(5+16+361-3)^2=143641

The (n+1)st term is the sum of the first n terms, minus n, all squared. Done.

Actually, I'm guessing this wasn't what you had in mind at all. :-P I'm posting this mostly in the hope that you will spoil at this point, since you apparently have stumped everyone for a couple of months now. :-)

2020-10-31, 07:12	#1
R2357 "Ruben" Oct 2020 Nederland 2×19 Posts	This one isn't in the OEIS Hello, New puzzle that I thought up : What sequence's representation starts with 5, 16, 361. It's not in the online encyclopedic integer sequences, so you will have to think a bit, then again, it's not quite challenging :)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
OEIS - A057732 : 2^n + 3	T.Rex	Miscellaneous Math	40	2015-09-15 14:01
OEIS - 2·A261539: (2^n+5)/3 , n even	T.Rex	Miscellaneous Math	38	2015-09-05 16:14
OEIS - A059242 : 2^n+5 , n odd	T.Rex	Miscellaneous Math	7	2015-08-28 18:04
my misunderstanding of the OEIS	science_man_88	Miscellaneous Math	11	2011-05-18 15:04

2021-01-12, 23:14	#2
TrojH Jan 2021 1₈ Posts	Hello. Newbie here. Looks pretty easy to me: (5-1)^2=16 (5+16-2)^2=361 (5+16+361-3)^2=143641 The (n+1)st term is the sum of the first n terms, minus n, all squared. Done. Actually, I'm guessing this wasn't what you had in mind at all. :-P I'm posting this mostly in the hope that you will spoil at this point, since you apparently have stumped everyone for a couple of months now. :-)