A374160
a(n) is the smallest nonnegative integer k where exactly n pairs of positive integers (x, y) exist such that x^2 + 11*y^2 = k.
Original entry on oeis.org
0, 12, 60, 180, 540, 1620, 2700, 8100, 12420, 20700, 37260, 1180980, 62100, 476100, 335340, 186300, 310500, 1822500, 558900, 53144100, 931500, 1676700, 4284900, 324860625, 1925100, 4657500, 244462860, 12854700, 8383500
Offset: 0
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from itertools import count
from sympy.abc import x,y
from sympy.solvers.diophantine.diophantine import diop_quadratic
def A374160(n): return next(m for m in count(0) if sum(1 for d in diop_quadratic(x**2+11*y**2-m) if d[0]>0 and d[1]>0)==n) # Chai Wah Wu, Jun 30 2024
A374159
a(n) is the smallest nonnegative integer k where exactly n pairs of positive integers (x, y) exist such that x^2 + 7*y^2 = k.
Original entry on oeis.org
0, 8, 32, 128, 352, 704, 1408, 2816, 5632, 11264, 16192, 45056, 32384, 123904, 64768, 178112, 129536, 2883584, 259072, 1982464, 469568, 712448, 1036288, 184549376, 939136, 21551552, 4145152, 2849792, 1878272
Offset: 0
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from itertools import count
from sympy.abc import x, y
from sympy.solvers.diophantine.diophantine import diop_quadratic
def A374159(n): return next(m for m in count(0) if sum(1 for d in diop_quadratic(x**2+7*y**2-m) if d[0]>0 and d[1]>0)==n) # Chai Wah Wu, Jun 30 2024
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.
Original entry on oeis.org
0, 20, 140, 700, 1540, 17500, 7700, 122500, 26180, 53900, 192500, 7035875, 130900, 592900, 4812500, 1347500, 602140, 150062500, 916300
Offset: 0
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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
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;
Showing 1-4 of 4 results.
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