A073526 Denominator of Sum_{k=1..n} 1/k^2 is a square.

1, 2, 3, 4, 5, 6, 7, 8, 9, 15, 16, 17, 18, 19, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 49, 75, 76, 77, 91, 92, 93, 94, 95, 96, 97, 98, 99, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 153, 154, 155, 205, 206, 207, 208, 209, 210, 211

Offset

1,2

Links

Table of n, a(n) for n=1..65.

Formula

{n: A007407(n) in A000290} . - R. J. Mathar, Oct 03 2014

Mathematica

Select[Range[300], IntegerQ[Sqrt[Denominator[Sum[1/k^2, {k, #}]]]]&] (* Harvey P. Dale, Mar 28 2012 *)

Crossrefs

Cf. A007407, A073527.

Sequence in context: A242415 A242420 A242419 * A032992 A190298 A069118

Adjacent sequences: A073523 A073524 A073525 * A073527 A073528 A073529

Keyword

nonn,easy

Author

N. J. A. Sloane, Aug 30 2002

Extensions

More terms from Matthew Conroy, Sep 09 2002

Status

approved