A250482 Numbers of the form 2^x + y^2, with x and y >=0.

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 16, 17, 18, 20, 24, 25, 26, 27, 29, 32, 33, 36, 37, 38, 40, 41, 44, 48, 50, 51, 52, 53, 57, 64, 65, 66, 68, 72, 73, 80, 81, 82, 83, 85, 89, 96, 97, 100, 101, 102, 104, 108, 113, 116, 122, 123, 125, 128, 129, 132, 137, 144

Offset: 1

Author

Vincenzo Librandi, Nov 24 2014

Keywords

• nonn

Comments

No terms are congruent to 7 mod 8: subsequence of A004777.

Examples

			12 is in this sequence because 2^3+2^2 = 12.
51 is in this sequence because 2^1+7^2 = 51.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..2500

Crossrefs

Cf. A004777, A250481.

Cf. sequences of the type k^x+y^k: this sequence (k=2), A250483 (k=3), A250545 (k=4), A250546 (k=5), A250547 (k=6), A250715 (k=7).

Programs

Mathematica

nn=15; Union[Select[Flatten[Table[2^x + y^2, {x, 0, nn}, {y, 0, nn}]], # <=nn^2 &]]

PARI

isok(n) = {k=0; while (2^k <= n, if (issquare(n - 2^k), return(1)); k++;); return (0);} \\ Michel Marcus, Nov 24 2014