A056650 a(n) is the greatest prime factor of a(n-1)^2+a(n-1)+1.

2, 7, 19, 127, 5419, 1009, 9181, 1423, 96493, 163350799, 25249969, 212520319916977, 784949209969, 145542538757017, 147660435988297, 2508855873622663, 3565137918692593, 6521735641, 11273204227, 16141059763, 125679599753438821, 240780337980146570229319, 7282590063606707136764017

Offset

0,1

Comments

Except for the first term the initial (ten at least) terms are one more than a multiple of 6, with the result that a(n)^2+a(n)+1 is in these cases an odd multiple of 3 and appears to be 3 times the product of primes all of which are one more than a multiple of 6.

Links

Dennis Langdeau, Table of n, a(n) for n = 0..31

Crossrefs

Cf. A031439, A045375.

Sequence in context: A126162 A054423 A137990 * A182169 A373765 A170869

Adjacent sequences: A056647 A056648 A056649 * A056651 A056652 A056653

Keyword

nonn

Author

Henry Bottomley, Aug 09 2000

Extensions

More terms from Vladeta Jovovic, Nov 26 2001

Status

approved