A374286 a(n) is the smallest nonnegative integer k where there are exactly n nonnegative integer solutions to x^2 + 3*y^2 = k.

2, 0, 4, 28, 1729, 196, 364, 1529437, 9604, 2548, 593047, 470596, 6916, 68574961, 33124, 124852, 1983163

Offset: 0

Author

Seiichi Manyama, Jul 02 2024

Keywords

• nonn
• more

Comments

a(n) is the smallest nonnegative k such that A119395(k) = n.

a(18) = 48412.

a(20) = 18384457.

a(21) = 6117748.

a(23) = 1623076.

a(24) = 214396.

a(27) = 629356.

a(30) = 2372188.

a(32) = 79530724.

a(36) = 1500772.

a(41) = 11957764.

a(42) = 116237212.

Crossrefs

Cf. A374285, A374288.

Cf. A119395, A374158.

Programs

PARI

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;