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A143427
a(n)=least prime == -1 mod 6 such that q(n)*(q(n)+a(n))-1 is prime with q(i)=i-th prime == 1 mod 6.
4
5, 5, 11, 11, 5, 5, 11, 23, 5, 11, 17, 41, 23, 5, 11, 17, 29, 17, 17, 11, 47, 41, 11, 11, 41, 11, 29, 41, 5, 11, 29, 17, 11, 5, 47, 17, 17, 53, 11, 5, 17, 17, 47, 29, 11, 23, 11, 5, 17, 5, 17, 29, 11, 17, 29, 11, 17, 5, 11, 17, 5, 17, 17, 29, 17, 17, 5, 23, 23, 11, 113, 17, 113, 5
OFFSET
1,1
EXAMPLE
q(1)=7, 7*(7+5)-1=83 prime, 5 prime == -1 mod 6 so a(1)=5
q(2)=13, 13*(13+5)-1=233 prime, so a(2)=5
q(3)=19, 19*(19+5)-1=455 composite 19*(19+11)-1=569 prime, 11 prime == -1 mod 6 so a(3)=11
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Aug 14 2008
STATUS
approved