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 A105935 #8 Sep 05 2019 11:23:09
%S A105935 6,12,18,20,21,33,36,42,54,57,60,65,87,93,99,100,104,105,108,111,141,
%T A105935 147,152,153,155,156,162,165,171,177,180,189,192,195,210,215,220,222,
%U A105935 230,235,238,240,249,255,261,264,273,276,279,280,286,294,295,297,300
%N A105935 Indices of Lucas 7-step numbers A104621 which have a nontrivial divisor in common with index.
%C A105935 Wanted: closed-form formula for this as exists for Fibonacci and Lucas numbers. Lucas 7-step numbers also known as heptanacci-Lucas numbers. The prime Lucas 7-step numbers are A105768, their indices being A104622.
%H A105935 Amiram Eldar, <a href="/A105935/b105935.txt">Table of n, a(n) for n = 1..10000</a>
%F A105935 gcd(a(n), A104621(a(n))) > 1.
%e A105935 gcd(a(n), A104621(6,12,18,33,36,57,60,87,93,108)) = 3,
%e A105935 gcd(a(n), A104621(20,65,100,105)) = 5,
%e A105935 gcd(a(n), A104621(21,42)) = 7,
%e A105935 gcd(a(n), A104621(54,99)) = 9,
%e A105935 gcd(a(n), A104621(104)) = 13.
%t A105935 m=300; s = LinearRecurrence[{1, 1, 1, 1, 1, 1, 1}, {7, 1, 3, 7, 15, 31, 63}, m+1]; Select[Range[m], !CoprimeQ[#, s[[#+1]]] &] (* _Amiram Eldar_, Sep 05 2019 *)
%Y A105935 Cf. A104621, A105285, A105289.
%K A105935 easy,nonn
%O A105935 1,1
%A A105935 _Jonathan Vos Post_, Apr 26 2005
%E A105935 Offset corrected and a(5)-a(6) and more terms added by _Amiram Eldar_, Sep 05 2019