

A175452


a(n) = smallest prime such that a(n)+2 is multiple of 2n+1.


0



7, 3, 5, 7, 31, 11, 13, 83, 17, 19, 67, 23, 79, 317, 29, 31, 103, 109, 37, 367, 41, 43, 139, 47, 151, 157, 53, 283, 293, 59, 61, 193, 199, 67, 211, 71, 73, 229, 709, 79, 911, 83, 433, 443, 89, 277, 283, 677, 97, 503, 101, 103, 2459, 107, 109, 337, 113, 349, 593, 1087
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OFFSET

1,1


COMMENTS

Terms appearing twice: a(1)=a(4)=7, a(5)=a(16)=31,...,
terms appearing thrice: a(28)=a(47)=a(142)=283, a(20)=a(61)=a(184)=367, etc.


LINKS

Table of n, a(n) for n=1..60.


EXAMPLE

n=1: 7+2 is multiple of 3, n=2: 3+2 is multiple of 5, n=5: 31+2 is multiple of 11, n=8: 83+2 is multiple of 17.


MATHEMATICA

s={}; Do[k=2; While[Mod[2+(p=Prime[k]), n]>0, k++ ]; AppendTo[s, p], {n, 3, 2001, 2}]; s


CROSSREFS

Cf. A124199.
Sequence in context: A154889 A135002 A319531 * A084714 A256779 A030760
Adjacent sequences: A175449 A175450 A175451 * A175453 A175454 A175455


KEYWORD

nonn


AUTHOR

Zak Seidov, May 16 2010


STATUS

approved



