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 A250327 #8 Jun 01 2022 20:31:09
%S A250327 1,5,180,2640,23100,157080,183260,2408560,317026710,10215305100,
%T A250327 89894684880,19613385792,403708857552,17825298787296,8681152006800,
%U A250327 435215087274240,2312080151144400,43249499297877600,45652249258870800,2835244953971976000,4394629678656562800
%N A250327 Numerator of the harmonic mean of the first n pentagonal numbers.
%H A250327 Colin Barker, <a href="/A250327/b250327.txt">Table of n, a(n) for n = 1..1000</a>
%e A250327 a(3) = 180 because the first 3 pentagonal numbers are [1,5,12] and 3/(1/1+1/5+1/12) = 180/77.
%t A250327 Table[Numerator[n/Total[1/PolygonalNumber[5,Range[n]]]],{n,30}] (* _Harvey P. Dale_, Jun 01 2022 *)
%o A250327 (PARI)
%o A250327 harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
%o A250327 s=vector(30); for(k=1, #s, s[k]=numerator(harmonicmean(vector(k, i, (3*i^2-i)/2)))); s
%Y A250327 Cf. A250328 (denominators).
%K A250327 nonn
%O A250327 1,2
%A A250327 _Colin Barker_, Nov 18 2014