A274577 Numbers n such that n is the sum of two nonzero squares while A006530(n) is not.

18, 72, 98, 162, 242, 245, 288, 392, 490, 605, 648, 722, 882, 968, 980, 1058, 1152, 1210, 1225, 1458, 1568, 1805, 1922, 1960, 2178, 2205, 2420, 2450, 2592, 2645, 2888, 3025, 3528, 3610, 3698, 3872, 3920, 4232, 4410, 4418, 4608, 4693, 4802, 4805, 4840, 4900, 5290

Offset

1,1

Links

Table of n, a(n) for n=1..47.

Example

245 is a term because 245 = 5*7^2 = 7^2 + 14^2 and 7 is not the sum of two nonzero squares.
1764 is not a term because 1764 = 2^2*3^2*7^2.

Mathematica

nR[n_]:=(SquaresR[2, n] + Plus@@Pick[{-4, 4}, IntegerQ/@ Sqrt[{n, n/2}]])/8; Select[ Range[10^4], nR[#] > 0 && Mod[FactorInteger[#][[-1, 1]], 4] == 3 &] (* Giovanni Resta, Jun 29 2016 *)

Crossrefs

Cf. A000404, A006530.

Sequence in context: A088490 A257693 A231328 * A347360 A373903 A195321

Adjacent sequences: A274574 A274575 A274576 * A274578 A274579 A274580

Keyword

nonn,easy

Author

Altug Alkan, Jun 29 2016

Status

approved