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 A284445 #18 Nov 26 2023 06:34:46
%S A284445 0,0,0,4,0,0,0,4,0,0,11,4,0,0,0,4,0,18,0,4,0,11,0,4,25,0,0,4,0,0,0,36,
%T A284445 11,0,0,22,0,0,39,4,0,0,0,15,0,46,0,4,0,25,0,4,53,18,11,4,0,0,0,64,0,
%U A284445 0,0,36,0,11,67,4,0,0,0,22,0,74,25,4,11,39,0,4,81
%N A284445 a(n) = Sum_{d|n, d == 4 (mod 7)} d.
%H A284445 Seiichi Manyama, <a href="/A284445/b284445.txt">Table of n, a(n) for n = 1..10000</a>
%F A284445 G.f.: Sum_{k>=0} (7*k + 4)*x^(7*k+4)/(1 - x^(7*k+4)). - _Ilya Gutkovskiy_, Mar 28 2017
%F A284445 Sum_{k=1..n} a(k) = c * n^2 + O(n*log(n)), where c = Pi^2/84 = 0.117495... . - _Amiram Eldar_, Nov 26 2023
%t A284445 Table[Sum[If[Mod[d, 7] == 4, d, 0], {d, Divisors[n]}], {n, 80}] (* _Indranil Ghosh_, Mar 27 2017 *)
%o A284445 (PARI) a(n) = sumdiv(n, d, d*((d % 7) == 4)); \\ _Amiram Eldar_, Nov 26 2023
%Y A284445 Cf. A109706.
%Y A284445 Cf. Sum_{d|n, d == k (mod 7)} d: A284099 (k=1), A284443 (k=2), A284444 (k=3), this sequence (k=4), A284446 (k=5), A284105 (k=6).
%K A284445 nonn,easy
%O A284445 1,4
%A A284445 _Seiichi Manyama_, Mar 27 2017