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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
Sequence in context: A088534 A178602 A363711 * A025441 A286813 A176891
KEYWORD
nonn
AUTHOR
V. Raman, Sep 03 2012
STATUS
approved

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Last modified February 24 02:58 EST 2024. Contains 370288 sequences. (Running on oeis4.)