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A155501
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Numbers n such that n^2 is of form x^2+40y^2 with positive x,y.
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2
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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
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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:= 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:
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CROSSREFS
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Cf. A155500 (numbers of form x^2+40y^2 with positive x, y).
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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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