A216279 Number of solutions to the equation x^2+5y^2 = n with x and y > 0.

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

Offset

1,21

Links

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

Prog

(PARI) a(n)=sum(k=1, sqrtint((n-1)\5), issquare(n-5*k^2)) \\ Charles R Greathouse IV, Jun 06 2016
(PARI) list(lim)=my(v=vector(lim\1), t); for(y=1, sqrtint((#v-1)\5), t=5*y^2; for(x=1, sqrtint(#v-t), v[x^2+t]++)); v \\ Charles R Greathouse IV, Jun 06 2016

Crossrefs

Cf. A092573, A119395, A000161, A025426.

Sequence in context: A088534 A178602 A363711 * A025441 A286813 A176891

Adjacent sequences: A216276 A216277 A216278 * A216280 A216281 A216282

Keyword

nonn

Author

V. Raman, Sep 03 2012

Status

approved