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A152466 a(1) = 252, a(n) is a(n-1) multiplied by the smallest prime factor of a(n-1)+1. 4
252, 2772, 130284, 651420, 219528540, 257067920340, 4370154645780, 292800361267260, 11023640801351071740, 13475008472558425746927448860, 5107028211099643358085503117940, 1313771981231475489737485570488833367540 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: this sequence will never have any numbers k where k+1 is prime. (All similar sequences that start with numbers less than 252 are known to have numbers k where k+1 is prime.)

The next few sequences that seem to be like this are 322, 622, 664, 776, and 830. - J. Lowell, Mar 25 2014

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 1..30

FORMULA

a(n) = A238642(a(n-1)) (conjectured). - J. Lowell, Mar 25 2014

EXAMPLE

First term is 252. Smallest prime factor of 253 is 11, so next term is 252 * 11 = 2772.

MATHEMATICA

a = {252}; Do[AppendTo[a, a[[ -1]]*FactorInteger[a[[ -1]] + 1][[1, 1]]], {10}]; a (* Stefan Steinerberger, Dec 06 2008 *)

NestList[#*FactorInteger[#+1][[1, 1]]&, 252, 20] (* Harvey P. Dale, Apr 03 2015 *)

CROSSREFS

Cf. A238584 (ratios of consecutive terms).

Sequence in context: A166783 A104679 A117281 * A004535 A027815 A271496

Adjacent sequences:  A152463 A152464 A152465 * A152467 A152468 A152469

KEYWORD

nonn

AUTHOR

J. Lowell, Dec 05 2008

EXTENSIONS

More terms from Stefan Steinerberger, Dec 06 2008

Extended by Max Alekseyev, Sep 19 2009

STATUS

approved

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Last modified November 15 11:35 EST 2018. Contains 317238 sequences. (Running on oeis4.)