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 A276967 #17 Sep 24 2016 03:19:37
%S A276967 1,3,9,15,21,33,39,51,57,63,69,87,93,111,123,129,141,159,177,183,195,
%T A276967 201,213,219,237,249,267,291,303,309,315,321,327,339,381,393,399,411,
%U A276967 417,447,453,471,489,501,519,537,543,573,579,591,597,633,669,681,687,693,699,717,723,731,753,771,789,807
%N A276967 Odd integers n such that 2^n == 2^3 (mod n).
%C A276967 Also, integers n such that 2^(n - 3) == 1 (mod n).
%C A276967 Contains A033553 as a subsequence. Smallest term greater than 3 missing in A033553 is 731.
%C A276967 For all m, 2^A015921(m) - 1 belongs to this sequence.
%H A276967 Seiichi Manyama, <a href="/A276967/b276967.txt">Table of n, a(n) for n = 1..10000</a>
%t A276967 Join[{1}, Select[Range[1, 1023, 2], PowerMod[2, # - 3, #] == 1 &]] (* _Alonso del Arte_, Sep 22 2016 *)
%o A276967 (PARI) isok(n) = (n % 2) && (Mod(2,n)^n==8); \\ _Michel Marcus_, Sep 23 2016
%Y A276967 The odd terms of A015922.
%Y A276967 Odd integers n such that 2^n == 2^k (mod n): A176997 (k = 1), A173572 (k = 2), this sequence (k = 3), A033984 (k = 4), A276968 (k = 5), A215610 (k = 6), A276969 (k = 7), A215611 (k = 8), A276970 (k = 9), A215612 (k = 10), A276971 (k = 11), A215613 (k = 12).
%K A276967 nonn,easy
%O A276967 1,2
%A A276967 _Max Alekseyev_, Sep 22 2016