

A129745


Numbers n such that Lucas(4n)/7 is prime.


0



5, 17, 19, 41, 43, 71, 1511, 2339, 3469, 4787, 7211, 9781
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

L(k) = Lucas(k) = Fibonacci(k1) + Fibonacci(k+1). 7 = L(4) divides L(4(1+2k)) since L(4n) = L(4)*L(4(n1))  L(4(n2)).
Integer n is in this sequence iff n is prime and 4n belongs to A085726. [From Max Alekseyev, May 16 2010]


LINKS

Table of n, a(n) for n=1..12.


MATHEMATICA

a=7; b=47; Do[ c=7ba; a=b; b=c; If[ PrimeQ[c/7], Print[n] ], {n, 3, 100}]


CROSSREFS

Cf. A000032, A001606 = Indices of prime Lucas numbers. Cf. A074304 = numbers n such that Lucas(2n)/3 is prime.
Sequence in context: A019349 A226627 A124873 * A304129 A038964 A019401
Adjacent sequences: A129742 A129743 A129744 * A129746 A129747 A129748


KEYWORD

less,more,nonn


AUTHOR

Alexander Adamchuk, May 14 2007, May 16 2007


EXTENSIONS

a(7)  a(10) from Stefan Steinerberger, May 17 2007
a(11) from Max Alekseyev, Nov 25 2007
a(12) from Alexander Adamchuk, May 15 2010


STATUS

approved



