OFFSET
1,1
COMMENTS
Ultraperfect numbers (A139306) minus 1.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..15
EXAMPLE
a(5) = 33554431 because A000043(5) = 13 and (2^(2*13 - 1))-1 = 2^25 - 1 = 33554431.
MATHEMATICA
2^(2 * MersennePrimeExponent[Range[10]] - 1) - 1 (* Amiram Eldar, Oct 17 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 13 2008, May 08 2008
STATUS
approved