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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. 0
1, 2, 5, 13, 17, 29, 421, 401, 37, 1877, 41 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
EXAMPLE
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.
Sequence in context: A160215 A068486 A099332 * A031439 A074856 A087952
KEYWORD
nonn,fini,full
AUTHOR
STATUS
approved

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Last modified March 29 04:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)