

A271430


Values of k such that L(k)*L(k+1)1 is a prime, where L(k) is the kth Lucas number (A000032).


1



1, 2, 5, 6, 8, 17, 18, 20, 26, 30, 45, 56, 156, 176, 306, 308, 548, 680, 1197, 2393, 2396, 3870, 4397, 7224, 9734, 17724, 25584, 31793, 44924, 70028, 79760, 91544, 96600
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OFFSET

1,2


COMMENTS

a(34) > 10^5.  Robert Price, Apr 17 2016


LINKS

Table of n, a(n) for n=1..33.


EXAMPLE

2 is in the sequence because L(2)*L(3)1 = 3*41 = 11, which is prime.


MATHEMATICA

Select[Range@ 5000, PrimeQ[LucasL@ # LucasL[# + 1]  1] &] (* Michael De Vlieger, Apr 07 2016 *)


PROG

(PARI)
lucas(n) = fibonacci(n+1) + fibonacci(n1)
L=List(); for(k=1, 1000, if(ispseudoprime(lucas(k)*lucas(k+1)1), listput(L, k))); Vec(L)


CROSSREFS

Cf. A000032, A271429.
Sequence in context: A079256 A191204 A191140 * A326854 A097685 A136369
Adjacent sequences: A271427 A271428 A271429 * A271431 A271432 A271433


KEYWORD

nonn,more


AUTHOR

Colin Barker, Apr 07 2016


EXTENSIONS

a(22)a(33) from Robert Price, Apr 17 2016


STATUS

approved



