OFFSET

1,6

COMMENTS

Lucas showed that A001602 divides p-1 or p+1, according as (5|p) = 1 or -1 respectively. This is the quotient.

LINKS

Patrick McKinley, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (prime(n) - (5|prime(n))) / A001602(n).

EXAMPLE

a(6) = 2, as 13 is the 6th prime, 5 is not a quadratic residue mod 13, 13 first occurs as a prime factor of Fibonacci(7) and (13 - (-1)) / 7 = 2.

CROSSREFS

KEYWORD

easy,nonn

AUTHOR

Nick Krempel, Mar 24 2006

EXTENSIONS

a(1)=1 added by N. J. A. Sloane, Dec 07 2020

STATUS

approved