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

1, 8, 108, 576, 18000, 21600, 1234800, 5644800, 57153600, 12700800, 1690476480, 1844156160, 337634256960, 363606122880, 1947889944000, 8310997094400, 2551995545299200, 2702112930316800, 1029655143835718400, 216769503965414400, 4645060799258880

Offset

1,2

Links

Colin Barker, Table of n, a(n) for n = 1..1000

Example

a(3) = 108 because the first 3 squares are [1,4,9] and 3 / (1/1+1/4+1/9) = 108/49.

Maple

A246498 := proc(n::integer)
    n/add(1/k^2, k=1..n) ;
    numer(%) ;
end proc:
seq(A246498(n), n=1..13) ; # R. J. Mathar, Nov 05 2019

Mathematica

Table[Numerator[n/Sum[1/k^2, {k, 1, n}]], {n, 1, 20}] (* Vaclav Kotesovec, Nov 14 2014 *)

Prog

(PARI)
harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
s=vector(30); for(k=1, #s, s[k]=numerator(harmonicmean(vector(k, i, i^2)))); s

Crossrefs

Cf. A007406 (denominators).

Sequence in context: A275134 A187190 A099762 * A119936 A276296 A164749

Adjacent sequences: A246495 A246496 A246497 * A246499 A246500 A246501

Keyword

nonn

Author

Colin Barker, Nov 14 2014

Status

approved