A140331 Smallest k such that 3^(3^n) - k is prime.

4, 2, 26, 10, 466, 506, 128, 13342, 5974, 8410

Offset

1,1

Comments

This is to 3 as A058220 is to 2.

Links

Table of n, a(n) for n=1..10.

Formula

a(n) = A064722(A055777(n)). - Michel Marcus, Jan 28 2015

Example

a(4) = 10 because 3^(3^4) - 10 = 443426488243037769948249630619149892793 is prime.

Mathematica

lst={}; Do[Do[p=3^(3^n)-k; If[PrimeQ[p], AppendTo[lst, k]; Break[]], {k, 2, 11!}], {n, 7}]; lst (* Vladimir Joseph Stephan Orlovsky, Apr 27 2010 *)

Prog

(PARI) a(n) = x = 3^(3^n); x - precprime(x); \\ Michel Marcus, Jan 28 2015

Crossrefs

Cf. A055777 (3^(3^n)), A058220.

Sequence in context: A228474 A058167 A372849 * A095896 A286798 A123670

Adjacent sequences: A140328 A140329 A140330 * A140332 A140333 A140334

Keyword

more,nonn

Author

Jonathan Vos Post, May 26 2008

Extensions

a(5)-a(8) from Cino Hilliard, Jun 02 2008

a(9)-a(10) from Donovan Johnson, Sep 13 2008

Status

approved