1,1

Maximilian Hasler (maximilian.hasler(AT)gmail.com), Apr 24 2008, observed that the numbers in this sequence are differences of two squares. For example: 3=2^2-1^2, 8=3^2-1^2, 9=5^2-4^2, 15=4^2-1^2, 16=5^2-3^2, 21=5^2-2^2, 24=5^2-1^2, 40=7^2-3^2, 45=7^2-2^2, 48=7^2-1^2, 60=8^2-2^2.

This sequence is a subset of A024352

Timing[f = 200; g = 300; h = 30; j = 100; b = {}; Do[a = {}; Do[Do[If[PrimeQ[x^2 + n y^2], AppendTo[a, x^2 + n y^2]], {x, 0, g}], {y, 1, g}]; AppendTo[b, Take[Union[a], h]], {n, 1, f}]; Print[b]; c = {}; Do[a = {}; Do[Do[If[PrimeQ[n^2 + w*n*m + m^2], AppendTo[a, n^2 + w*n*m + m^2]], {n, m, g}], {m, 1, g}]; AppendTo[c, Take[Union[a], h]], {w, 1, j}]; Print[c]; bb = {}; cc = {}; Do[Do[If[b[[p]] == c[[q]], AppendTo[bb, p]; AppendTo[cc, q]], {p, 1, f}], {q, 1, j}]; Union[bb]] (*Artur Jasinski*)

Adjacent sequences: A139488 A139489 A139490 this_sequence A139492 A139493 A139494

Sequence in context: A071677 A084747 A101065 this_sequence A080517 A099256 A025615

Cf. A024352.

more,nonn,new

Artur Jasinski (grafix(AT)csl.pl), Apr 24 2008, Apr 26 2008