OFFSET
1,1
LINKS
Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
EXAMPLE
10 belongs to this sequence as both 9*10 - 1 = 89 and 10* 11 - 1 = 109 are primes.
PROG
(PARI) isok(k) = isprime(k^2+k-1) && isprime(k^2-k-1); \\ Michel Marcus, Nov 19 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Apr 02 2003
EXTENSIONS
More terms from Don Reble, Apr 08 2003
STATUS
approved