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A246498 Numerator of the harmonic mean of the first n squares.

%I A246498 #12 Nov 05 2019 04:41:50
%S A246498 1,8,108,576,18000,21600,1234800,5644800,57153600,12700800,1690476480,
%T A246498 1844156160,337634256960,363606122880,1947889944000,8310997094400,
%U A246498 2551995545299200,2702112930316800,1029655143835718400,216769503965414400,4645060799258880
%N A246498 Numerator of the harmonic mean of the first n squares.
%H A246498 Colin Barker, <a href="/A246498/b246498.txt">Table of n, a(n) for n = 1..1000</a>
%e A246498 a(3) = 108 because the first 3 squares are [1,4,9] and 3 / (1/1+1/4+1/9) = 108/49.
%p A246498 A246498 := proc(n::integer)
%p A246498     n/add(1/k^2,k=1..n) ;
%p A246498     numer(%) ;
%p A246498 end proc:
%p A246498 seq(A246498(n),n=1..13) ; # _R. J. Mathar_, Nov 05 2019
%t A246498 Table[Numerator[n/Sum[1/k^2,{k,1,n}]],{n,1,20}] (* _Vaclav Kotesovec_, Nov 14 2014 *)
%o A246498 (PARI)
%o A246498 harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
%o A246498 s=vector(30); for(k=1, #s, s[k]=numerator(harmonicmean(vector(k, i, i^2)))); s
%Y A246498 Cf. A007406 (denominators).
%K A246498 nonn
%O A246498 1,2
%A A246498 _Colin Barker_, Nov 14 2014