A374286
a(n) is the smallest nonnegative integer k where there are exactly n nonnegative integer solutions to x^2 + 3*y^2 = k.
Original entry on oeis.org
2, 0, 4, 28, 1729, 196, 364, 1529437, 9604, 2548, 593047, 470596, 6916, 68574961, 33124, 124852, 1983163
Offset: 0
-
b(n, k) = sum(i=0, sqrtint(n), sum(j=0, sqrtint(n\k), i^2+k*j^2==n));
a(n, k=3) = my(cnt=0); while(b(cnt, k)!=n, cnt++); cnt;
A374288
a(n) is the smallest nonnegative integer k where there are exactly n nonnegative integer solutions to x^2 + 5*y^2 = k.
Original entry on oeis.org
2, 0, 9, 81, 189, 441, 1449, 10206, 3969, 12789, 13041, 35721, 30429, 194481, 117369, 115101, 186921, 2893401, 273861
Offset: 0
-
b(n, k) = sum(i=0, sqrtint(n), sum(j=0, sqrtint(n\k), i^2+k*j^2==n));
a(n, k=5) = my(cnt=0); while(b(cnt, k)!=n, cnt++); cnt;
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