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%I #10 Jun 07 2023 08:52:11
%S 1,7,63,2047,1048575,137438953471,1180591620717411303423,
%T 43556142965880123323311949751266331066367,
%U 29642774844752946028434172162224104410437116074403984394101141506025761187823615
%N a(n) = 2^(2^n+n) - 1.
%C 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.
%H Wilfrid Keller, <a href="https://doi.org/10.1090/S0025-5718-1995-1308456-3">New Cullen Primes</a>, Mathematics of Computation, Vol. 64, No. 212 (Ocober 1995), pp. 1733-1741.
%F a(n) = 2^(2^n+n)-1 = A000225(2^n+n) = A003261(2^n).
%e The fourth integer which is both a Mersenne number and a Woodall number is 2047. Hence a(3)=2047 (as the offset is zero).
%t 2^(2^#+#)-1 &/@Range[0,8]
%Y Cf. A000225, A003261, A006127.
%K easy,nonn
%O 0,2
%A _Ant King_, Feb 12 2008