OFFSET
1,2
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000 (n = 1..1000 from Robert Israel)
MAPLE
filter:= proc(y) local S;
S:= map(t -> subs(t, x), [isolve(x*(x+1)+y*(y+1)=z*(z+1))]);
select(t -> t>0 and t<=y, S) = []
end proc:
select(filter, [$1..300]); # Robert Israel, Aug 06 2019
MATHEMATICA
max = 500; lst = {}; For[x = 1, x < max, x++,
For[y = x, y < max, y++,
For[z = y, z < max, z++,
If[x (x + 1) + y (y + 1) == z (z + 1),
lst = AppendTo[lst, y]]]]]; lst =
Select[Union[lst], # < max/2 &]; Complement[Range[Length[lst]], lst]
PROG
(Python)
from sympy import integer_nthroot
A309388_list, y, w = [], 1, 0
while len(A309388_list) < 10000:
w += y
z = 0
for x in range(1, y+1):
z += x
if integer_nthroot(8*(w+z)+1, 2)[1]:
break
else:
A309388_list.append(y)
y += 1 # Chai Wah Wu, Aug 07 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Ralf Steiner, Aug 02 2019
STATUS
approved