1,1

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

10 belongs to this sequence as both 9*10 - 1 = 89 and 10* 11 - 1 = 109 are primes.

(PARI) isok(k) = isprime(k^2+k-1) && isprime(k^2-k-1); \\ Michel Marcus, Nov 19 2019

Cf. A081945.

Sequence in context: A338321 A220844 A047250 * A129948 A050414 A342469

Adjacent sequences: A081941 A081942 A081943 * A081945 A081946 A081947

nonn

Amarnath Murthy, Apr 02 2003

More terms from Don Reble, Apr 08 2003

approved