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 A130061 #14 Sep 21 2024 02:26:49
%S A130061 1,3,35,147,195,219,291,399,579,583,723,939,1011,1023,1227,1299,1371,
%T A130061 1443,1731,1803,2019,2307,2499,2811,3003,3027,3099,3387,3459,3603,
%U A130061 3747,3891,3963,4467,4623,4827,4971,5187,5259,5331,5403,5619,5979,6051,6267
%N A130061 Numbers k that divide 3^((k-1)/2) - 2^((k-1)/2) - 1.
%C A130061 It appears that all terms are composite except a(1) = 1 and a(2) = 3. Most listed terms are divisible by 3, except {1, 35, 583, 70643, ...}.
%H A130061 Amiram Eldar, <a href="/A130061/b130061.txt">Table of n, a(n) for n = 1..10000</a>
%t A130061 Select[ Range[10000], Mod[ PowerMod[3,(#-1)/2,# ] - PowerMod[2,(#-1)/2,# ] -1, # ]==0&]
%Y A130061 Cf. A097934 (primes p that divide 3^((p-1)/2) - 2^((p-1)/2)).
%Y A130061 Cf. A038876 (primes p such that 6 is a square mod p).
%Y A130061 Cf. A127071, A127072, A127073, A127074.
%Y A130061 Cf. A130058, A130059, A130060, A130062, A130063.
%K A130061 nonn
%O A130061 1,2
%A A130061 _Alexander Adamchuk_, May 05 2007