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 A006971 M5461 #37 Nov 06 2023 07:17:14
%S A006971 561,1105,1729,1905,2047,2465,4033,4681,6601,8321,8481,10585,12801,
%T A006971 15841,16705,18705,25761,30121,33153,34945,41041,42799,46657,52633,
%U A006971 62745,65281,74665,75361,85489,87249,90751,113201,115921,126217,129921,130561,149281,158369
%N A006971 Composite numbers k such that k == +-1 (mod 8) and 2^((k-1)/2) == 1 (mod k).
%C A006971 Previous name was "Terms of A047713 that are congruent to +-1 mod 8".
%C A006971 Complement of (A244626 union A244628) with respect to A047713. - _Jianing Song_, Sep 18 2018
%D A006971 Richard K. Guy, Unsolved Problems in Number Theory, 3rd Edition, Springer, 2004, Section A12, pp. 44-50.
%D A006971 Hans Riesel, Prime numbers and computer methods for factorization, Progress in Mathematics, Vol. 57, Birkhäuser, Boston, 1985.
%D A006971 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A006971 Amiram Eldar, <a href="/A006971/b006971.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..828 from Jianing Song using data from A047713)
%t A006971 Select[Range[10^5], MemberQ[{1, 7}, Mod[#, 8]] && CompositeQ[#] && PowerMod[2, (# - 1)/2, #] == 1 &] (* _Amiram Eldar_, Nov 06 2023 *)
%Y A006971 Subsequence of A001567 and A047713.
%Y A006971 Cf. A244626, A244628, A270697, A270698.
%K A006971 nonn
%O A006971 1,1
%A A006971 _Richard Pinch_
%E A006971 This sequence appeared as M5461 in Sloane-Plouffe (1995), but was later mistakenly declared to be an erroneous form of A047713. Thanks to _Jianing Song_ for providing the correct definition. - _N. J. A. Sloane_, Sep 17 2018
%E A006971 Formal definition by _Jianing Song_, Sep 18 2018