A186720 As p runs through the primes, sequence gives denominator of Sum_{k=1..p-1} 1/k^2.

1, 4, 144, 3600, 1270080, 153679680, 519437318400, 150117385017600, 221193371393280, 6450247552370862240000, 5424658191543895143840000, 20852386088294732932920960000, 28546916554875489385168794240000, 6855338104106528236638391873920000, 12675520154492970709544386574878080000

Offset: 1

Author

N. J. A. Sloane, Jan 21 2012

Keywords

• nonn

References

• Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See pp. 22-23.

Links

• R. Mestrovic, Wolstenholme's theorem: Its Generalizations and Extensions in the last hundred and fifty years (1862-2011), arXiv:1111.3057 [math.NT], 2011.

Crossrefs

Cf. A125551, A061002.

Programs

Maple

f2:=proc(n) local p;
p:=ithprime(n);
denom(add(1/i^2,i=1..p-1));
end proc;
[seq(f2(n),n=1..20)];

Mathematica

a[n_] := HarmonicNumber[Prime[n] - 1, 2] // Denominator;
Array[a, 15] (* Jean-François Alcover, Nov 25 2017 *)