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 A279663 #9 Feb 16 2025 08:33:38
%S A279663 1,1,8,208,12480,1435200,281299200,86640153600,39507910041600,
%T A279663 25482601976832000,22424689739612160000,26147188236387778560000,
%U A279663 39429959860472770068480000,75350653293363463600865280000,179334554838205043370059366400000,523656900127558726640573349888000000
%N A279663 a(n) = (5/6)^n*Gamma(n+3/5)*Gamma(n+1)*Gamma(n+2)/Gamma(3/5).
%C A279663 Heptagonal pyramidal factorial numbers.
%H A279663 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeptagonalPyramidalNumber.html">Heptagonal Pyramidal Number</a>
%H A279663 <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a>
%H A279663 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>
%F A279663 a(n) = Product_{k=1..n} k*(k + 1)*(5*k - 2)/6, a(0)=1.
%F A279663 a(n) = Product_{k=1..n} A002413(k), a(0)=1.
%F A279663 a(n) ~ (2*Pi)^(3/2)*(5/6)^n*n^(3*n+21/10)/(Gamma(3/5)*exp(3*n)).
%t A279663 FullSimplify[Table[(5/6)^n Gamma[n + 3/5] Gamma[n + 1] Gamma[n + 2]/Gamma[3/5], {n, 0, 15}]]
%o A279663 (Magma) [Round((5/6)^n*Gamma(n+3/5)*Gamma(n+1)*Gamma(n+2)/Gamma(3/5)): n in [0..20]]; // _Vincenzo Librandi_ Dec 17 2016
%Y A279663 Cf. A002413.
%Y A279663 Cf. A084940 (heptagonal factorial numbers).
%Y A279663 Cf. A087047 (tetrahedral factorial numbers), A135438 (square pyramidal factorial numbers), A167484 (pentagonal pyramidal factorial numbers), A279662 (hexagonal pyramidal factorial numbers).
%K A279663 nonn
%O A279663 0,3
%A A279663 _Ilya Gutkovskiy_, Dec 16 2016