The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A098915 Least k such that k*Mersenne-prime(n)*Mersenne-prime(n+1) - 1 is prime. 0
 2, 2, 2, 24, 2, 50, 6, 26, 14, 306, 86, 846, 104, 1832, 272, 2222, 2540, 884, 5474, 1950, 28358, 13338, 76740 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 2*(2^2-1)*(2^3-1) - 1 = 41 is prime, so a(1) = 2. 2*(2^3-1)*(2^5-1) - 1 = 433 is prime, so a(2) = 2. MATHEMATICA f[n_] := Module[{k = 1}, While[!PrimeQ[k*n - 1], k++]; k]; f /@ Times @@@ Partition[2^MersennePrimeExponent[Range[15]] - 1, 2, 1] (* Amiram Eldar, Jul 24 2021 *) CROSSREFS Cf. A000043, A000668. Sequence in context: A067097 A260082 A153438 * A095855 A157979 A147975 Adjacent sequences: A098912 A098913 A098914 * A098916 A098917 A098918 KEYWORD nonn,more AUTHOR Pierre CAMI, Oct 17 2004 EXTENSIONS a(15)-a(23) from Amiram Eldar, Jul 24 2021 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 28 21:15 EDT 2023. Contains 361596 sequences. (Running on oeis4.)