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A118664 Least prime p such that n*(p#^2)-1 is prime or 0 if n is a square so no prime possible. 0
2, 2, 2, 0, 2, 2, 3, 2, 0, 3, 2, 2, 3, 3, 2, 0, 2, 2, 3, 2, 2, 269, 3, 3, 0, 2, 2, 7, 5, 29, 11, 2, 2, 3, 2, 0, 11, 2, 5, 3, 2, 2, 5, 3, 2, 5, 5, 2, 0, 2, 17, 3, 2, 11, 3, 2, 2, 3, 7, 2, 7, 5, 2, 0, 3, 2, 3, 2, 5, 7, 2, 3, 5, 3, 3, 5, 2, 2, 3, 3, 0, 41, 2, 3, 7, 7, 2, 3, 3, 2, 5, 2, 3, 53, 2, 2, 3, 3, 7, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..100.

EXAMPLE

1*(2^2)-1=3 prime so a(1)=2

7*(2^2)-1=27 composite

7*((2*3)^2)-1=251 prime so a(7)=3

CROSSREFS

Sequence in context: A328995 A036476 A104994 * A223175 A322213 A118205

Adjacent sequences:  A118661 A118662 A118663 * A118665 A118666 A118667

KEYWORD

nonn

AUTHOR

Pierre CAMI, May 19 2006

STATUS

approved

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Last modified October 24 19:11 EDT 2020. Contains 338009 sequences. (Running on oeis4.)