A135630 2^(prime(n) - 2) - 1.

0, 1, 7, 31, 511, 2047, 32767, 131071, 2097151, 134217727, 536870911, 34359738367, 549755813887, 2199023255551, 35184372088831, 2251799813685247, 144115188075855871, 576460752303423487, 36893488147419103231, 590295810358705651711

Offset: 1

Author

Omar E. Pol, Mar 01 2008

Keywords

• easy
• nonn

Examples

			a(4)=31 because the 4th prime number is 7 and 7-2=5 and 2^5=32 and 32-1=31.
		

Links

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

Crossrefs

Cf. A000040, A040976, A061286.

Programs

Magma

[2^(NthPrime(n)-2)-1: n in [1..30]]; // Vincenzo Librandi, Sep 06 2014

Mathematica

Table[2^(Prime[n]-2)-1,{n,20}]  (* Harvey P. Dale, Feb 25 2011 *)

Formula

a(n) = 2^(A000040(n)-2) - 1 = 2^(A040976(n)) - 1 = (2^A000040(n)/4) - 1 = (A061286(n)/2) - 1.

Extensions

More terms from Harvey P. Dale, Feb 25 2011