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 A107639 Smallest prime a such that (a*b)^2 + a*b -1 is prime with b prime = 2^(2*n) - 2^n - 1, see A098845 for n. 0
 5, 7, 31, 11, 5, 3, 809, 661, 139, 73, 521, 701, 131, 487, 89, 211, 733, 3011, 311, 8837, 2837, 8831, 1733, 401, 983, 17881, 1783, 19553, 13859 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 2^4-2^2-1=3=b(1) prime, (3*3)^2+3*3-1=89 prime so a(1)=3 2^8-2^4-1=239=b(2) prime, (7*239)^2+7*239-1=2800601 prime so a(2)=7 CROSSREFS Cf. A098845. Sequence in context: A081630 A307532 A135324 * A069688 A158323 A025119 Adjacent sequences:  A107636 A107637 A107638 * A107640 A107641 A107642 KEYWORD hard,more,nonn AUTHOR Pierre CAMI, Jun 10 2005 STATUS approved

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Last modified August 10 02:24 EDT 2020. Contains 336365 sequences. (Running on oeis4.)