This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A366818 #13 Oct 22 2024 05:43:01
%S A366818 4,16,192,2304,5160960,1010565120,14467203072,148764064972013568,
%T A366818 87162491526879729295140036437606400,
%U A366818 4304762755241260838085244444377946703587691074682880,246056756234946697892331840382404519263272106760845744463151104,227937183538024006739312962615527377661237903932985846822055286571232395264
%N A366818 Let p = A000043(n) be the n-th Mersenne exponent, then a(n) = ((2^p-1)^2-1)/p.
%C A366818 a(n) is the largest k such that 2 is a k-th power in the finite field F_{2^p-1}(i), where i^2 = -1.
%H A366818 Amiram Eldar, <a href="/A366818/b366818.txt">Table of n, a(n) for n = 1..15</a>
%e A366818 In F_9 = F_3(i), we have 2 = (1+i)^2.
%e A366818 Jn F_49 = F_7(i), we have 2 = (3+i)^16.
%e A366818 In F_961 = F_31(i), we have 2 = (5+4*i)^192.
%o A366818 (PARI) A366818(lim) = my(q); forprime(p=2, lim, if(isprime(q=2^p-1), print1((q^2-1)/p, ", ")))
%Y A366818 Cf. A000043, A000668.
%K A366818 nonn
%O A366818 1,1
%A A366818 _Jianing Song_, Oct 24 2023