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%I #16 Nov 25 2017 16:31:27
%S 1,4,144,3600,1270080,153679680,519437318400,150117385017600,
%T 221193371393280,6450247552370862240000,5424658191543895143840000,
%U 20852386088294732932920960000,28546916554875489385168794240000,6855338104106528236638391873920000,12675520154492970709544386574878080000
%N As p runs through the primes, sequence gives denominator of Sum_{k=1..p-1} 1/k^2.
%H R. Mestrovic, <a href="http://arxiv.org/abs/1111.3057">Wolstenholme's theorem: Its Generalizations and Extensions in the last hundred and fifty years (1862-2011)</a>, arXiv:1111.3057 [math.NT], 2011.
%p f2:=proc(n) local p;
%p p:=ithprime(n);
%p denom(add(1/i^2,i=1..p-1));
%p end proc;
%p [seq(f2(n),n=1..20)];
%t a[n_] := HarmonicNumber[Prime[n] - 1, 2] // Denominator;
%t Array[a, 15] (* _Jean-François Alcover_, Nov 25 2017 *)
%Y Cf. A125551, A061002.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Jan 21 2012
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