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

1,2

Links

Table of n, a(n) for n=1..15.

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

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 *)

Crossrefs

Cf. A125551, A061002.

Sequence in context: A134631 A036511 A263386 * A060870 A268894 A084703

Adjacent sequences: A186717 A186718 A186719 * A186721 A186722 A186723

Keyword

nonn

Author

N. J. A. Sloane, Jan 21 2012

Status

approved