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A031440 a(0)=3 and for n>0 a(n) is the greatest prime factor of a(n-1)^2 - 2. 2
3, 7, 47, 2207, 4481, 26111, 189017, 67271, 11815633, 606737, 708641, 354023, 125332284527, 51939720282500417, 18062107820423, 1376080289340623571113, 4012316132900773615751, 983669740542169, 4443427285129103, 19744046038229790810567377584607, 4300749014896245437702886338812998834884967953, 41572359968343362282287450730112204489086145685200294134959430572332688727999 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Is this sequence unbounded? [Charles R Greathouse IV, Dec 29 2011]

LINKS

Dennis Langdeau, Table of n, a(n) for n = 0..23

MATHEMATICA

NestList[FactorInteger[#^2-2][[-1, 1]]&, 3, 22] (* Harvey P. Dale, Jan 10 2013 *)

CROSSREFS

Sequence in context: A020754 A052381 A219877 * A001566 A173771 A019039

Adjacent sequences:  A031437 A031438 A031439 * A031441 A031442 A031443

KEYWORD

nonn,nice

AUTHOR

Yasutoshi Kohmoto

EXTENSIONS

More terms from Dennis Langdeau (dlangdea(AT)sfu.ca), Jun 26 2006

STATUS

approved

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Last modified October 15 15:33 EDT 2018. Contains 316236 sequences. (Running on oeis4.)