OFFSET
1,1
COMMENTS
If the map "x -> smallest odd prime divisor of n^2+1" is iterated, does it always terminate in the 2-cycle (5 <-> 13)? - Zoran Sunic, Oct 25 2017
REFERENCES
Richard Friedberg, An Adventurer's Guide to Number Theory, McGraw-Hill, NY, 1968.
Popular Computing (Calabasas, CA), Friedberg's Sequence, Vol. 5 (No. 46, Jan 1977), page PC46-2.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
MATHEMATICA
Table[FactorInteger[4*n^2+1][[1, 1]], {n, 59}] (* Ivan N. Ianakiev, Apr 20 2015 *)
PROG
(Haskell)
a256970 = a020639 . a053755 -- Reinhard Zumkeller, Apr 20 2015
(PARI) a(n) = factor(4*n^2+1)[1, 1]; \\ Michel Marcus, Apr 20 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 19 2015
STATUS
approved