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%I M2504 #16 Aug 26 2015 01:06:36
%S 1,3,5,17,65537
%N (2^2^...^2) (n times) + 1.
%C a(0) could equally well be taken to be 2 rather than 1, which gives A004249. - _N. J. A. Sloane_, Sep 14 2009
%C The next term already has 19729 digits and is too large to include. - _Stefan Steinerberger_, Apr 14 2006
%D P. Ribenboim, The Book of Prime Number Records. Springer-Verlag, NY, 2nd ed., 1989, p. 73.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%F a(1) = 1, a(2) = 3, a(n+1) = 2^(a(n)-1) + 1. - _Stefan Steinerberger_, Apr 14 2006
%t a[1] := 1; a[2] := 3; a[n_] := 2^(a[n - 1] - 1) + 1; Table[a[n], {n, 1, 5}] (* _Stefan Steinerberger_, Apr 14 2006 *)
%Y Cf. A004249 (another version).
%K nonn
%O 0,2
%A _N. J. A. Sloane_ and _Robert G. Wilson v_
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