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 A361691 #119 Jun 25 2023 10:39:44
%S A361691 1,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,2,1,1,3,1,1,1,
%T A361691 1,1,2,1,2,1,2,1,3,1,1,1,2,1,2,1,1,1,1,2,3,1,1,2,1,1,2,1,3,1,1,1,3,1,
%U A361691 1,1,2,1,3,1,1,1,1,1,3,2,1,1,2,1,3,1,2,2,1,1,2,1,2,1,2,1,2,1,1,1
%N A361691 Number of divisors of 7*n-1 of form 7*k+1.
%C A361691 Also number of divisors of 7*n-1 of form 7*k+6.
%F A361691 a(n) = A279061(7*n-1) = A363808(7*n-1).
%F A361691 G.f.: Sum_{k>0} x^(6*k-5)/(1 - x^(7*k-6)).
%F A361691 G.f.: Sum_{k>0} x^k/(1 - x^(7*k-1)).
%t A361691 a[n_] := DivisorSum[7*n - 1, 1 &, Mod[#, 7] == 1 &]; Array[a, 100] (* _Amiram Eldar_, Jun 25 2023 *)
%o A361691 (PARI) a(n) = sumdiv(7*n-1, d, d%7==1);
%Y A361691 Cf. A363854, A363855, A363856, A363857, A363858.
%Y A361691 Cf. A279061, A363808.
%K A361691 nonn
%O A361691 1,7
%A A361691 _Seiichi Manyama_, Jun 24 2023