OFFSET
1,1
COMMENTS
Primes p congruent to +2 or -2 (mod 5) divide Fibonacci(p+1) (cf. A003631 and [Hardy and Wright]).
REFERENCES
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers (Fifth edition), Oxford Univ. Press (Clarendon), 1979, Chap. X, p. 150.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..2000 (n = 1..250 from Reinhard Zumkeller, n = 251..1000 from Giovanni Resta)
FORMULA
Fibonacci(2*a(n)) mod a(n) = a(n) - 1. - Gary Detlefs, May 26 2014
MATHEMATICA
Select[Range[2, 100000], !PrimeQ[#]&&Divisible[Fibonacci[#+1], #]&] (* Harvey P. Dale, Sep 18 2011 *)
PROG
(Haskell)
a069107 n = a069107_list !! (n-1)
a069107_list = h 2 $ drop 3 a000045_list where
h n (fib:fibs) = if fib `mod` n > 0 || a010051 n == 1
then h (n+1) fibs else n : h (n+1) fibs
-- Reinhard Zumkeller, Oct 13 2011
(PARI) is(n)=((Mod([1, 1; 1, 0], n))^(n+1))[1, 2]==0 && !isprime(n) && n>1 \\ Charles R Greathouse IV, Oct 07 2016
CROSSREFS
KEYWORD
nice,nonn
AUTHOR
Benoit Cloitre, Apr 06 2002
EXTENSIONS
Corrected by Ralf Stephan, Oct 17 2002
STATUS
approved