A188713 Primes of the form 2^x + 2^y - 1.

2, 3, 5, 7, 11, 17, 19, 23, 31, 47, 67, 71, 79, 127, 131, 191, 257, 263, 271, 383, 1031, 1039, 1087, 1151, 1279, 2063, 2111, 4099, 4111, 4127, 4159, 5119, 6143, 8191, 8447, 16447, 20479, 32771, 32783, 32831, 33023, 33791, 65537

Offset

1,1

Links

Ivan Neretin, Table of n, a(n) for n = 1..1000

Example

2^2 + 2^2 - 1 = 7;
2^2 + 2^3 - 1 = 11.

Mathematica

f[x_, y_] := 2^x + 2^y - 1; imax = 20; lst= {}; Do[p = f[x, y]; If[p < 2^imax && PrimeQ[p], AppendTo[lst, p]], {y, 0, imax}, {x, 0, y}]; lst (* Orlovski *)
nn=20; Select[Flatten[Table[2^x + 2^y - 1, {x, 0, nn}, {y, 0, x}]], #<2^nn && PrimeQ[#]&] (* Alonso del Arte, Apr 09 2011 *)

Crossrefs

Cf. A070739.

Sequence in context: A042989 A333872 A302493 * A280996 A377544 A089084

Adjacent sequences: A188710 A188711 A188712 * A188714 A188715 A188716

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Apr 08 2011

Status

approved