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 A103777 Numbers n such that f[n],f[n+1]and f[n+2] are all primes, where f[n]=8*n^2+4*n+1. 1
 15, 50, 80, 110, 230, 245, 425, 570, 635, 645, 710, 925, 1440, 1645, 1710, 1815, 2000, 2465, 2635, 2940, 3040, 3090, 3195, 3525, 4260, 4310, 4400, 4885, 5960, 6145, 7030, 7120, 7250, 8430, 8890, 9445, 10265, 11060, 11150, 11710, 11775, 13020, 13565 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are divisible by 5, hence conjecture: there is no such n that f[n],f[n+1],f[n+2] and f[n+3] are primes. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 EXAMPLE 15 is a term because f[15]=1861, f[16]=2113 and f[17]=2381 are all primes. MATHEMATICA Flatten[Position[Partition[Table[PrimeQ[8n^2+4n+1], {n, 14000}], 3, 1], {True, True, True}]] (* Harvey P. Dale, Oct 08 2012 *) CROSSREFS Cf. A102083, A103776. Sequence in context: A199899 A020257 A298511 * A134742 A318084 A191746 Adjacent sequences:  A103774 A103775 A103776 * A103778 A103779 A103780 KEYWORD nonn AUTHOR Zak Seidov, Feb 15 2005 STATUS approved

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Last modified March 29 15:16 EDT 2020. Contains 333107 sequences. (Running on oeis4.)