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A153090 Least k(n) such that k(n)*3^n*(3^n-1)+j is prime with j= -1 or 1 or both. 2
1, 1, 1, 1, 3, 1, 1, 14, 5, 5, 5, 1, 7, 6, 5, 7, 12, 1, 5, 1, 6, 29, 23, 20, 8, 6, 23, 9, 2, 15, 18, 19, 13, 57, 1, 1, 9, 10, 15, 16, 22, 12, 26, 5, 5, 6, 39, 41, 6, 9, 50, 6, 32, 20, 4, 8, 2, 79, 28, 23, 33, 78, 31, 35, 19, 32, 46, 7, 6, 116, 39, 18, 20, 6, 35, 8, 25, 39, 31, 26, 117, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Sum a(n) for n=1 to k / sum n for n=1 to k tends to 2*log(3)/7.

LINKS

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

EXAMPLE

1*3^1*(3^1-1)-1=5 prime as 7 so k(1)=1 1*3^2*(3^2-1)-1=71 prime as 73 so k(2)=1

CROSSREFS

Cf. A152414, A152091, A152092, A152093, A152094, A152095.

Sequence in context: A015112 A174690 A156869 * A203002 A073483 A006956

Adjacent sequences:  A153087 A153088 A153089 * A153091 A153092 A153093

KEYWORD

nonn

AUTHOR

Pierre CAMI, Dec 18 2008

STATUS

approved

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Last modified April 24 09:54 EDT 2019. Contains 322420 sequences. (Running on oeis4.)