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A025342
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Numbers that are the sum of 3 distinct nonzero squares in exactly 4 ways.
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1
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161, 189, 194, 209, 234, 254, 261, 270, 281, 285, 290, 293, 299, 321, 362, 365, 369, 371, 378, 386, 390, 395, 401, 405, 406, 419, 429, 449, 450, 465, 469, 477, 482, 485, 489, 491, 501, 510, 518, 534, 539, 557, 563, 570, 573, 574, 586, 589, 601, 609, 633, 644, 645, 649
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listen;
history;
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internal format)
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OFFSET
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1,1
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LINKS
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MAPLE
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N:= 10^6;
A:= Vector(N):
for a from 1 to floor(sqrt(N/3)) do
for b from a+1 to floor(sqrt((N-a^2)/2)) do
c:= [$(b+1) .. floor(sqrt(N-a^2-b^2))]:
v:= map(t -> a^2 + b^2 + t^2, c):
A[v]:= map(`+`, A[v], 1)
od od:
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MATHEMATICA
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Sort[Transpose[Select[Tally[Total/@Subsets[Range[30]^2, {3}]], #[[2]]==4&]][[1]]] (* Harvey P. Dale, Apr 24 2013 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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