# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a007516 Showing 1-1 of 1 %I A007516 M2504 #16 Aug 26 2015 01:06:36 %S A007516 1,3,5,17,65537 %N A007516 (2^2^...^2) (n times) + 1. %C A007516 a(0) could equally well be taken to be 2 rather than 1, which gives A004249. - _N. J. A. Sloane_, Sep 14 2009 %C A007516 The next term already has 19729 digits and is too large to include. - _Stefan Steinerberger_, Apr 14 2006 %D A007516 P. Ribenboim, The Book of Prime Number Records. Springer-Verlag, NY, 2nd ed., 1989, p. 73. %D A007516 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %F A007516 a(1) = 1, a(2) = 3, a(n+1) = 2^(a(n)-1) + 1. - _Stefan Steinerberger_, Apr 14 2006 %t A007516 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 A007516 Cf. A004249 (another version). %K A007516 nonn %O A007516 0,2 %A A007516 _N. J. A. Sloane_ and _Robert G. Wilson v_ # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE