A239527 Numbers k^2 + (k+1)^2 that can be expressed as a sum of two squares in exactly one other way.

85, 145, 221, 265, 365, 481, 545, 685, 1405, 1513, 1985, 2245, 2813, 2965, 3281, 3785, 3961, 4141, 4705, 5305, 5513, 5941, 6161, 6385, 6613, 7081, 7813, 8065, 8321, 9113, 9385, 10805, 11101, 11401, 11705, 12013, 12961, 13285, 13945, 16021, 17113, 17861, 19405

Offset: 1

Author

Carmine Suriano, Mar 21 2014

Keywords

• nonn

Comments

Subsequence of A166080.

Examples

			365 is in the sequence because 365 = 2^2+19^2 = 13^2+14^2; in the second representation 14-13=1.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A166080, A000404, A001844.

Programs

Mathematica

ok[n_] := 2 == Count[ PowersRepresentations[n, 2, 2], ?(! MemberQ[#, 0] &)]; Select[(2*#^2 + 2*# + 1) & /@ Range[100], ok] (* _Giovanni Resta, Mar 21 2014 *)

Formula

Each number is of the form 2y^2 + 2y + 1.