A134487 a(1)=1; for n>=2, a(n) = the largest prime dividing n*a(n-1) + 1.

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

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 A356026

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