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A143394 Least prime a(n) such that a(n)*(a(n)+p(n))-1 and a(n)*(a(n)+p(n))+1 are twin primes or 0 if not such prime exist, with p(i)=i-th prime. 2
0, 3, 0, 2, 3, 2, 3, 2, 109, 1291, 3, 557, 211, 3, 3, 7, 7, 3, 2, 13, 2, 5, 43, 97, 2, 3, 149, 43, 5, 3, 5, 13, 3, 2, 7, 3, 5, 197, 13, 73, 7, 11, 229, 23, 3, 5, 3, 23, 13, 2, 19, 7, 5, 109, 283, 67, 7, 3, 11, 13, 2, 43, 2, 19, 233, 7, 1061, 3, 3, 149, 43, 421, 11, 113, 29, 7, 991, 41, 61 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

no first of twin primes of the form a*(a+2)-1 for a prime

only one first of twin primes of the form a*(a+3)-1 for a=3

no first of twin primes of the form a*(a+5)-1 for a prime

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..12250

EXAMPLE

3*(3+3)-1=17 prime so a(2)=3 as p(2)=3 and 17 and 19 twin primes

CROSSREFS

Cf. A143393.

Sequence in context: A154574 A119493 A032531 * A112455 A001608 A159977

Adjacent sequences:  A143391 A143392 A143393 * A143395 A143396 A143397

KEYWORD

nonn

AUTHOR

Pierre CAMI (pierre-cami(AT)bbox.fr), Aug 12 2008

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Last modified February 16 04:47 EST 2012. Contains 205860 sequences.