A374161 a(n) is the smallest nonnegative integer k where exactly n pairs of positive integers (x, y) exist such that x^2 + 19*y^2 = k.

0, 20, 140, 700, 1540, 17500, 7700, 122500, 26180, 53900, 192500, 7035875, 130900, 592900, 4812500, 1347500, 602140, 150062500, 916300

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Prog

(Python)
from itertools import count
from sympy.abc import x, y
from sympy.solvers.diophantine.diophantine import diop_quadratic
def A374161(n): return next(m for m in count(0) if sum(1 for d in diop_quadratic(x**2+19*y**2-m) if d[0]>0 and d[1]>0)==n) # Chai Wah Wu, Jun 30 2024

Crossrefs

Cf. A328151, A343105, A374158, A374159, A374160.

Sequence in context: A134382 A105939 A054389 * A253003 A293932 A071816

Adjacent sequences: A374158 A374159 A374160 * A374162 A374163 A374164

Keyword

nonn,more

Author

Seiichi Manyama, Jun 29 2024

Status

approved