A137810 a(n) = 2^(2^n+n) - 1.

1, 7, 63, 2047, 1048575, 137438953471, 1180591620717411303423, 43556142965880123323311949751266331066367, 29642774844752946028434172162224104410437116074403984394101141506025761187823615

Offset

0,2

Comments

An integer is simultaneously a Mersenne number and a Woodall number if and only if it is a member of this sequence. Hence this sequence is the intersection of A000225 and A003261.

Links

Table of n, a(n) for n=0..8.

Wilfrid Keller, New Cullen Primes, Mathematics of Computation, Vol. 64, No. 212 (Ocober 1995), pp. 1733-1741.

Formula

a(n) = 2^(2^n+n)-1 = A000225(2^n+n) = A003261(2^n).

Example

The fourth integer which is both a Mersenne number and a Woodall number is 2047. Hence a(3)=2047 (as the offset is zero).

Mathematica

2^(2^#+#)-1 &/@Range[0, 8]

Crossrefs

Cf. A000225, A003261, A006127.

Sequence in context: A152797 A345383 A126883 * A316577 A036287 A116231

Adjacent sequences: A137807 A137808 A137809 * A137811 A137812 A137813

Keyword

easy,nonn

Author

Ant King, Feb 12 2008

Status

approved