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A098570

Least k such that Mersenne-prime(n)*prime(k)# - 1 is prime, where prime(k)# is the k-th primorial.

1, 1, 1, 2, 1, 3, 1, 10, 9, 7, 9, 7, 36, 105, 375, 120, 280, 226, 1215, 263, 2098, 310, 2330

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OFFSET

1,4

LINKS

Table of n, a(n) for n=1..23.

MATHEMATICA

f[p_] := Module[{m = 1, k = 2, q = 2}, While[!PrimeQ[k*p - 1], q = NextPrime[q]; k *= q; m++]; m]; f /@ (2^MersennePrimeExponent[Range[15]] - 1) (* Amiram Eldar, Jul 25 2021 *)

CROSSREFS

Cf. A000043, A000668, A002110, A098571.

Sequence in context: A301935 A237978 A337276 * A122048 A046208 A195909

Adjacent sequences: A098567 A098568 A098569 * A098571 A098572 A098573

KEYWORD

nonn,more

AUTHOR

Pierre CAMI, Sep 16 2004

EXTENSIONS

a(21)-a(23) from Amiram Eldar, Jul 25 2021

STATUS

approved

URL: https://oeis.org/A098570

⇱ A098570 - OEIS