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A134487 a(1)=1; for n>=2, a(n) = the largest prime dividing n*a(n-1) + 1. 2
1, 3, 5, 7, 3, 19, 67, 179, 31, 311, 59, 709, 419, 5867, 557, 2971, 61, 157, 373, 829, 1741, 38303, 2381, 1039, 191, 4967, 13411, 375509, 418837, 966547, 14981479, 16127, 16631, 149, 163, 5869, 15511, 829, 137, 29, 17, 13, 7, 103, 61, 401, 31, 1489 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

a(9)=31 because 9*a(8) + 1 = 9*179 + 1 = 1612 = 2*2*13*31.

MAPLE

with(numtheory): a:=proc(n) local f, L: if n = 1 then 1 else f:=factorset(1+n*a(n-1)): L:=convert(f, list): L[nops(L)] end if end proc: seq(a(n), n=1..35); # Emeric Deutsch, Nov 12 2007

MATHEMATICA

a = {1}; Do[AppendTo[a, FactorInteger[(Length[a] + 1)*a[[ -1]] + 1][[ -1, 1]]], {70}]; a (* Stefan Steinerberger, Oct 30 2007 *)

nxt[{a_, n_}]:={FactorInteger[a(n+1)+1][[-1, 1]], n+1}; Transpose[ NestList[ nxt, {1, 1}, 50]][[1]] (* Harvey P. Dale, Jun 02 2014 *)

CROSSREFS

Cf. A134486.

Sequence in context: A130139 A204938 A101088 * A064537 A023899 A279321

Adjacent sequences:  A134484 A134485 A134486 * A134488 A134489 A134490

KEYWORD

nonn

AUTHOR

Leroy Quet, Oct 28 2007

EXTENSIONS

More terms from Stefan Steinerberger, Oct 30 2007

STATUS

approved

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Last modified February 17 16:15 EST 2018. Contains 299296 sequences. (Running on oeis4.)