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 A098817 a(n) is the least k such that k*Mersenne_prime(n)^2 - 1 and k*Mersenne_prime(n)^2 + 1 are twin primes. 0
 2, 18, 72, 780, 228, 852, 228, 1080, 4020, 25800, 6012, 40332, 713502, 332880, 455892, 6428118, 4142652, 173808 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..18. EXAMPLE 2*((2^2-1)^2) - 1 = 17, 2*((2^2-1)^2) + 1 = 19; 17 and 19 are twin primes so a(1) = 2. MATHEMATICA f[p_] := Module[{k = 1}, While[!PrimeQ[k*p^2 - 1] || !PrimeQ[k*p^2 + 1], k++]; k]; f /@ (2^MersennePrimeExponent[Range[10]] - 1) (* Amiram Eldar, Aug 28 2021 *) CROSSREFS Cf. A000043, A000668, A001097. Sequence in context: A120361 A120358 A152887 * A197093 A034473 A024171 Adjacent sequences: A098814 A098815 A098816 * A098818 A098819 A098820 KEYWORD nonn,more AUTHOR Pierre CAMI, Oct 08 2004 EXTENSIONS a(7) corrected, a(12) inserted and a(15)-a(18) added by Amiram Eldar, Aug 28 2021 STATUS approved

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Last modified September 22 00:10 EDT 2023. Contains 365503 sequences. (Running on oeis4.)