

A181515


Greatest k < n such that 3^n  3^k  1 is prime, or 0 if no such prime exists.


4



0, 1, 2, 3, 2, 4, 0, 7, 8, 4, 7, 10, 12, 7, 10, 12, 13, 15, 17, 17, 20, 16, 15, 23, 17, 8, 3, 27, 24, 22, 19, 23, 25, 23, 30, 35, 13, 31, 22, 30, 21, 39, 17, 37, 32, 40, 42, 45, 45, 43, 45, 50, 50, 48, 34, 53, 56, 0, 54, 25
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OFFSET

1,3


LINKS

Pierre CAMI, Table of n, a(n) for n = 1..2000


MAPLE

A181515 := proc(n) local p, k; for k from n1 to 1 by 1 do p := 3^n3^k1 ; if isprime(p) then return k; end if; end do: return 0 ; end proc: # R. J. Mathar, Jan 30 2011


MATHEMATICA

Table[Max[Flatten[Position[3^n3^Range[n1]1, _?PrimeQ]]], {n, 60}]/.\[Infinity]>0 (* Harvey P. Dale, Feb 12 2011 *)


CROSSREFS

Sequence in context: A167504 A286013 A208083 * A183045 A060847 A079528
Adjacent sequences: A181512 A181513 A181514 * A181516 A181517 A181518


KEYWORD

nonn


AUTHOR

Pierre CAMI, Jan 29 2011


STATUS

approved



