A155501 Numbers n such that n^2 is of form x^2+40y^2 with positive x,y.

7, 11, 13, 14, 19, 21, 22, 23, 26, 28, 33, 35, 37, 38, 39, 41, 42, 44, 46, 47, 49, 52, 53, 55, 56, 57, 59, 63, 65, 66, 69, 70, 74, 76, 77, 78, 82, 84, 88, 89, 91, 92, 94, 95, 98, 99, 103, 104, 105, 106, 110, 111, 112, 114, 115, 117, 118, 119, 121, 123, 126, 127, 130, 131

Offset: 1

Author

Zak Seidov, Jan 23 2009

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A155500 (numbers of form x^2+40y^2 with positive x, y).

Programs

Maple

N:= 1000: # to get all terms <= N
g:= proc(t) local r; if t^2 > 40*y^2 then return NULL fi;
r:= t/2 + 20*y^2/t; if r::integer and r <= N then r fi; end proc:
R:= {}:
for y from 1 to floor(N/sqrt(40)) do
  R:= R union map(g, numtheory:-divisors(40*y^2))
od:
sort(convert(R,list)); # Robert Israel, Jul 16 2018