A025391 Numbers that are the sum of 4 distinct nonzero squares in 7 or more ways.

190, 198, 210, 222, 231, 238, 246, 255, 270, 282, 286, 290, 294, 302, 303, 306, 310, 315, 318, 326, 330, 334, 335, 338, 342, 345, 350, 351, 354, 357, 358, 363, 366, 369, 370, 374, 375, 378, 381, 382, 385, 386, 387, 390, 393, 394, 398, 399, 402, 405, 406, 407, 410, 411

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to sums of squares

Crossrefs

Cf. A025372.

Programs

Maple

N:= 1000: # for terms <= N
G:= mul(1+x^(i^2)*y, i=1..floor(sqrt(N))):
G4:= series(coeff(G,y,4),x,N+1):
A:= select(t -> coeff(G4,x,t) >= 7, [$1..N]); # Robert Israel, Nov 19 2023

Mathematica

With[{nn=25},Select[Select[Tally[Total/@Subsets[Range[nn]^2,{4}]],#[[2]]> 6&][[All,1]]//Union,#<=(nn^2-14)&]] (* Harvey P. Dale, Jun 21 2021 *)

Formula

{n: A025443(n) >= 7}. - R. J. Mathar, Jun 15 2018