A279882 a(n) = 2^(prime(n) + 1) - 1.

7, 15, 63, 255, 4095, 16383, 262143, 1048575, 16777215, 1073741823, 4294967295, 274877906943, 4398046511103, 17592186044415, 281474976710655, 18014398509481983, 1152921504606846975, 4611686018427387903, 295147905179352825855, 4722366482869645213695

Offset: 1

Author

Jaroslav Krizek, Dec 21 2016

Keywords

• nonn
• easy

Comments

Numbers whose binary representation is 1 repeated (prime(n)+1) times.

The only prime term is 7.

Examples

			For n=3; a(3) = 2^(prime(3) + 1) - 1 = 2^(5 + 1) - 1 = 2^6 - 1 = 63.
		

Crossrefs

Cf. A101304 (2^(prime(n)+1)+1), A098102 (2^(prime(n)-1)-1), A278741 (2^(prime(n)-1)+1).

Programs

Magma

[2^(NthPrime(n)+1)-1: n in[1..50]]

Maple

A279882:=n->2^(ithprime(n)+1)-1: seq(A279882(n), n=1..30); # Wesley Ivan Hurt, Jan 23 2017

Mathematica

f[n_] := 2^(Prime[n]+1)-2; Array[f, 20] (* Robert G. Wilson v, Dec 21 2016 *)
2^(Prime[Range[20]]+1)-1 (* Harvey P. Dale, Jul 29 2024 *)

PARI

a(n) = 2^(prime(n)+1)-1 \\ Felix Fröhlich, Dec 21 2016

Formula

a(n) = A101304(n) - 2.

a(n) = A000225(A008864(n)). - Felix Fröhlich, Dec 21 2016