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 A346581 #7 Jul 25 2021 02:41:27
%S A346581 1,6,63,728,9275,124866,1753073,25365600,375677595,5667202850,
%T A346581 86775157139,1345153422600,21069043965983,332927798516614,
%U A346581 5301031234076325,84967018610221440,1369846562874360886,22199151535757655354,361411377745122110421,5908312923789590118600
%N A346581 a(n) = (1/(7*n)) * Sum_{d|n} mu(n/d) * binomial(7*d,d).
%C A346581 Inverse Euler transform of A002296.
%C A346581 Moebius transform of A261500.
%t A346581 Table[(1/(7 n)) Sum[MoebiusMu[n/d] Binomial[7 d, d], {d, Divisors[n]}], {n, 20}]
%o A346581 (PARI) a(n) = sumdiv(n, d, moebius(n/d)*binomial(7*d,d))/(7*n); \\ _Michel Marcus_, Jul 24 2021
%Y A346581 Cf. A002296, A004368, A008683, A022553, A261500, A346577, A346578, A346579, A346580, A346582.
%K A346581 nonn
%O A346581 1,2
%A A346581 _Ilya Gutkovskiy_, Jul 24 2021