A279687 a(0) = 1, a(n) is the least prime factor of a(n-1)^2+1 that has not previously appeared in the sequence for n > 0.

1, 2, 5, 13, 17, 29, 421, 401, 37, 1877, 41

Offset: 0

Author

Franklin T. Adams-Watters, Dec 17 2016

Keywords

• nonn
• fini
• full

Examples

			a(7) is a prime factor of a(6)^2+1 = 421^2 + 1 = 177242, which factors as 2*13*17*401. 2, 13, and 17 have already appeared in the sequence, so a(7) = 401.
a(10)^2+1 = 882 = 2 * 29^2. Both 2 and 29 have already appeared in the sequence, so it terminates.
		

Crossrefs

Cf. A031439.