A098640 a(n) = 2^p + 1 where p is the n-th prime.

5, 9, 33, 129, 2049, 8193, 131073, 524289, 8388609, 536870913, 2147483649, 137438953473, 2199023255553, 8796093022209, 140737488355329, 9007199254740993, 576460752303423489, 2305843009213693953

Offset: 1

Author

Parthasarathy Nambi, Oct 27 2004

Keywords

• nonn
• easy

Examples

			If p=2, 2^2+1 = 5.
If p=7, 2^7+1 = 129.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A184084.

Programs

Magma

[2^p+1: p in PrimesUpTo(100)]; // Vincenzo Librandi, Apr 29 2014

Mathematica

Table[2^Prime[n] + 1, {n, 18}] (* Robert G. Wilson v, Nov 01 2004 *)

PARI

a(n) = 2^prime(n) + 1; \\ Amiram Eldar, Nov 22 2022

Formula

Product_{n>=1} (1 - 1/a(n)) = A184084. - Amiram Eldar, Nov 22 2022

Extensions

More terms from Robert G. Wilson v, Nov 01 2004