

A016104


2^2^2^ ... 2^w (with n 2's), where w = 1.92878.....


1




OFFSET

0,2


COMMENTS

w is uniquely defined as the largest value such that for all n>0, a(n) is prime.  Charles R Greathouse IV, Oct 25 2006
Wright's paper uses this as an example, although the sequence is not welldefined there. The next term is probably 2^1638235411, a 4932digit prp.  Charles R Greathouse IV, Oct 25 2006 [Update March 2019: Samuel S. Wagstaff, Jr proves the primality of a(4), see the Baillie link for details.  Charles R Greathouse IV, Mar 27 2019]


LINKS

Table of n, a(n) for n=0..3.
Robert Baillie, Wright's Fourth Prime, arXiv:1705.09741 [math.NT], 2017.
Aminu Alhaji Ibrahim, Sa’idu Isah Abubaka, Aunu Integer Sequence as NonAssociative Structure and Their Graph Theoretic Properties, Advances in Pure Mathematics, 2016, 6, 409419.
Simon Plouffe, The calculation of p(n) and pi(n), arXiv:2002.12137 [math.NT], 2020.
P. Ribenboim, Prime number records, TwoYear College Math. Jnl., 25 (1994), pp. 280290.
E. M. Wright, A primerepresenting function, Amer. Math. Monthly, 58 (1951), 616618.


FORMULA

a(0) = 1, a(n) = the greatest prime less than 2^(a(n1)+1).  Charles R Greathouse IV, Oct 25 2006


CROSSREFS

Cf. A086238.
Sequence in context: A127855 A087333 A320041 * A112856 A007523 A092830
Adjacent sequences: A016101 A016102 A016103 * A016105 A016106 A016107


KEYWORD

nonn


AUTHOR

Robert G. Wilson v


STATUS

approved



