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A016104 2^2^2^ ... 2^w (with n 2's), where w = 1.92878..... 1
1, 3, 13, 16381 (list; graph; refs; listen; history; text; internal format)



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 well-defined there. The next term is probably 2^16382-35411, a 4932-digit 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]


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 Non-Associative Structure and Their Graph Theoretic Properties, Advances in Pure Mathematics, 2016, 6, 409-419.

Simon Plouffe, The calculation of p(n) and pi(n), arXiv:2002.12137 [math.NT], 2020.

P. Ribenboim, Prime number records, Two-Year College Math. Jnl., 25 (1994), pp. 280-290.

E. M. Wright, A prime-representing function, Amer. Math. Monthly, 58 (1951), 616-618.


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


Cf. A086238.

Sequence in context: A127855 A087333 A320041 * A112856 A007523 A092830

Adjacent sequences:  A016101 A016102 A016103 * A016105 A016106 A016107




Robert G. Wilson v



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Last modified August 8 04:32 EDT 2020. Contains 336290 sequences. (Running on oeis4.)