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A216279 Number of solutions to the equation x^2+5y^2 = n with x and y > 0. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A230264 A088534 A178602 * A025441 A286813 A176891

Adjacent sequences:  A216276 A216277 A216278 * A216280 A216281 A216282

KEYWORD

nonn

AUTHOR

V. Raman, Sep 03 2012

STATUS

approved

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Last modified December 13 12:42 EST 2019. Contains 329968 sequences. (Running on oeis4.)