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 A363859 #12 Sep 05 2025 15:43:58
%S A363859 1,0,1,1,1,0,2,0,1,1,1,0,3,0,1,1,1,0,2,0,1,2,2,0,2,0,1,1,1,0,3,0,2,1,
%T A363859 1,0,2,0,2,2,1,0,3,0,1,1,1,0,3,0,1,1,2,0,3,1,1,2,1,0,2,0,2,1,1,0,3,0,
%U A363859 1,1,2,0,4,0,1,2,1,0,3,0,1,1,2,0,3,0,2,1,1,1,2,0,2,2,1,0,2,0,1,1
%N A363859 Number of divisors of 7*n-1 of the form 7*k+2.
%C A363859 Also number of divisors of 7*n-1 of form 7*k+3.
%F A363859 a(n) = A363795(7*n-1) = A363805(7*n-1).
%F A363859 G.f.: Sum_{k>0} x^(3*k-2)/(1 - x^(7*k-5)).
%F A363859 G.f.: Sum_{k>0} x^(2*k-1)/(1 - x^(7*k-4)).
%F A363859 a(n) = Sum_{d|(7n-1)} c((d-2)/7), where c(n) = 1-ceiling(n)+floor(n). - _Wesley Ivan Hurt_, Sep 05 2025
%t A363859 a[n_] := DivisorSum[7*n - 1, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* _Amiram Eldar_, Jun 25 2023 *)
%o A363859 (PARI) a(n) = sumdiv(7*n-1, d, d%7==2);
%Y A363859 Cf. A363795, A363805.
%K A363859 nonn,changed
%O A363859 1,7
%A A363859 _Seiichi Manyama_, Jun 24 2023