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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: A088534 A178602 A363711 * 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 February 24 02:58 EST 2024. Contains 370288 sequences. (Running on oeis4.)