

A117522


Numbers k such that L(2*k + 1) is prime, where L(m) is a Lucas number.


15



2, 3, 5, 6, 8, 9, 15, 18, 20, 23, 26, 30, 35, 39, 56, 156, 176, 251, 306, 308, 431, 548, 680, 2393, 2396, 2925, 3870, 4233, 5345, 6125, 6981, 7224, 9734, 17724, 18389, 22253, 25584, 28001, 40835, 44924, 47411, 70028, 74045
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OFFSET

1,1


COMMENTS

For n = 24..43, we can only claim that L(2*a(n) + 1) is a probable prime. Sequence arises in a study of A269254; for detailed theory, see [Hone].  L. Edson Jeffery, Feb 09 2018


LINKS

Table of n, a(n) for n=1..43.
Andrew N. W. Hone, et al., On a family of sequences related to Chebyshev polynomials, arXiv:1802.01793 [math.NT], 2018.


EXAMPLE

If k = 56, then L(2*k + 1) is a prime with twentyfour digits.


CROSSREFS

Cf. A000032, A001606, A269251, A269252, A269253, A269254.
Cf. A294099, A298675, A298677, A298878, A299045, A299071, A285992, A299107, A299109, A088165, A299100, A299101, A113501.
Sequence in context: A153775 A173666 A063756 * A299101 A335658 A294941
Adjacent sequences: A117519 A117520 A117521 * A117523 A117524 A117525


KEYWORD

nonn,hard


AUTHOR

Parthasarathy Nambi, Apr 26 2006


EXTENSIONS

Values beyond 680 from L. Edson Jeffery, et al., Feb 02 2018


STATUS

approved



