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 A317980 #24 Sep 17 2020 17:11:31
%S A317980 2,10,70,700,8400,126000,2142000,42840000,942480000,23562000000,
%T A317980 636174000000,19085220000000,610727040000000,21375446400000000,
%U A317980 790891516800000000,31635660672000000000,1328697748224000000000,59791398670080000000000,2810195737493760000000000
%N A317980 a(n) = Product_{i=1..n} floor(5*i/2).
%C A317980 If p > 2 and p is odd, then Product_{i=1..n} floor(p*i/2) ~ (p/2)^n * n! * 2^(1/(2*p)) * sqrt(Pi) / (Gamma(1/2 - 1/(2*p)) * n^(1/(2*p))).
%H A317980 Harvey P. Dale, <a href="/A317980/b317980.txt">Table of n, a(n) for n = 1..390</a>
%F A317980 a(n) ~ (5/2)^n * n! * 2^(1/10) * sqrt(Pi) / (Gamma(2/5) * n^(1/10)).
%F A317980 Recurrence: 4*a(n) - 10*a(n-1) - 5*(n - 1)*(5*n - 6)*a(n-2) = 0, with n >= 3. - _Bruno Berselli_, Oct 03 2018
%t A317980 Table[Product[Floor[i*5/2], {i, 1, n}], {n, 1, 20}]
%t A317980 RecurrenceTable[{4 a[n] - 10 a[n - 1] - 5 (n - 1) (5 n - 6) a[n - 2] == 0, a[1] == 2, a[2] == 10}, a, {n, 1, 20}] (* _Bruno Berselli_, Oct 03 2018 *)
%t A317980 FoldList[Times,Floor[5*Range[20]/2]] (* _Harvey P. Dale_, Sep 17 2020 *)
%Y A317980 Cf. A010786, A180736, A275062, A319948, A319950.
%K A317980 nonn
%O A317980 1,1
%A A317980 _Vaclav Kotesovec_, Oct 02 2018