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A186720
As p runs through the primes, sequence gives denominator of Sum_{k=1..p-1} 1/k^2.
2
1, 4, 144, 3600, 1270080, 153679680, 519437318400, 150117385017600, 221193371393280, 6450247552370862240000, 5424658191543895143840000, 20852386088294732932920960000, 28546916554875489385168794240000, 6855338104106528236638391873920000, 12675520154492970709544386574878080000
OFFSET
1,2
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
Sequence in context: A134631 A036511 A263386 * A060870 A268894 A084703
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 21 2012
STATUS
approved