A216579 Number of positive integer solutions to the equation a^2 + 10*b^2 = n.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2

Offset

1,91

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

a[ n_] := If[ n < 1, 0, Length@Select[ Range@Sqrt[ n/10], IntegerQ@Sqrt[ n - 10 #] &]]; (* Michael Somos, Jan 10 2015 *)

Prog

(PARI) a(n)=sum(b=1, sqrtint((n-1)\10), issquare(n-10*b^2)) \\ Charles R Greathouse IV, Nov 19 2014

Crossrefs

Cf. A020673, A033201.

Sequence in context: A112802 A137979 A160338 * A229878 A235145 A266342

Adjacent sequences: A216576 A216577 A216578 * A216580 A216581 A216582

Keyword

nonn

Author

V. Raman, Sep 08 2012

Status

approved