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A098819 Least k such that k*(Mersenne_prime(n)^2) + 1 is prime. 0
2, 4, 16, 12, 22, 28, 30, 22, 138, 12, 102, 180, 426, 1444, 9502, 6568, 2212, 5380, 9942, 3034, 24222, 31530, 2962, 7848, 93280, 3718 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A035092. - Amiram Eldar, Mar 01 2019

LINKS

Table of n, a(n) for n=1..26.

EXAMPLE

2*((2^2-1)^2)+1=19 prime so a(1)=2.

MATHEMATICA

a[n_] := Module[{k = 1, m = (2^MersennePrimeExponent[n] - 1)^2}, While[! PrimeQ[k*m + 1], k++]; k]; Array[a, 20] (* Amiram Eldar, Mar 01 2019 *)

CROSSREFS

Cf. A000043, A000668, A035092.

Sequence in context: A186110 A073923 A153666 * A186008 A067846 A155893

Adjacent sequences:  A098816 A098817 A098818 * A098820 A098821 A098822

KEYWORD

more,nonn

AUTHOR

Pierre CAMI, Oct 08 2004

EXTENSIONS

a(19)-a(22) from Donovan Johnson, Mar 23 2008

a(23)-a(26) from Amiram Eldar, Mar 01 2019

STATUS

approved

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Last modified May 25 03:50 EDT 2019. Contains 323539 sequences. (Running on oeis4.)