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A025372
Numbers that are the sum of 4 nonzero squares in 7 or more ways.
7
130, 135, 138, 148, 150, 154, 162, 170, 172, 175, 178, 180, 182, 183, 186, 187, 189, 190, 195, 196, 198, 199, 202, 207, 210, 213, 214, 215, 217, 218, 220, 222, 223, 225, 226, 228, 229, 230, 231, 234, 235, 237, 238, 242, 243, 244, 245, 246, 247, 250, 252, 253, 255, 258
OFFSET
1,1
FORMULA
{n: A025428(n) >= 7}. - R. J. Mathar, Jun 15 2018
MAPLE
N:= 1000: # for terms <= N
B:= Vector(N):
for i from 1 while 4*i^2 <= N do
for j from i while i^2 + 3*j^2 <= N do
for k from j while i^2 + j^2 + 2*k^2 <= N do
for l from k do
m:= i^2 + j^2 + k^2 + l^2;
if m > N then break fi;
B[m]:= B[m]+1
od od od od:
select(t -> B[t] >= 7, [$1..N]); # Robert Israel, Oct 23 2020
CROSSREFS
KEYWORD
nonn
STATUS
approved