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A139307
a(n) = (2^(2*p - 1)) - 1, where p is A000043(n).
4
7, 31, 511, 8191, 33554431, 8589934591, 137438953471, 2305843009213693951, 2658455991569831745807614120560689151, 191561942608236107294793378393788647952342390272950271
OFFSET
1,1
COMMENTS
Ultraperfect numbers (A139306) minus 1.
LINKS
FORMULA
a(n) = (2^(2*A000043(n) - 1)) - 1 = A139306(n) - 1.
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