A139307 a(n) = (2^(2*p - 1)) - 1, where p is A000043(n).

7, 31, 511, 8191, 33554431, 8589934591, 137438953471, 2305843009213693951, 2658455991569831745807614120560689151, 191561942608236107294793378393788647952342390272950271

Offset: 1

Author

Omar E. Pol, Apr 13 2008, May 08 2008

Keywords

• nonn

Comments

Ultraperfect numbers (A139306) minus 1.

Examples

			a(5) = 33554431 because A000043(5) = 13 and (2^(2*13 - 1))-1 = 2^25 - 1 = 33554431.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..15

Crossrefs

Cf. A000043, A139287, A139295, A139306.

Programs

Mathematica

2^(2 * MersennePrimeExponent[Range[10]] - 1) - 1 (* Amiram Eldar, Oct 17 2024 *)

Formula

a(n) = (2^(2*A000043(n) - 1)) - 1 = A139306(n) - 1.