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A132850 a(0)=1; a(n) = the smallest prime dividing (n+a(n-1)), for n>=1. 1
1, 2, 2, 5, 3, 2, 2, 3, 11, 2, 2, 13, 5, 2, 2, 17, 3, 2, 2, 3, 23, 2, 2, 5, 29, 2, 2, 29, 3, 2, 2, 3, 5, 2, 2, 37, 73, 2, 2, 41, 3, 2, 2, 3, 47, 2, 2, 7, 5, 2, 2, 53, 3, 2, 2, 3, 59, 2, 2, 61, 11, 2, 2, 5, 3, 2, 2, 3, 71, 2, 2, 73, 5, 2, 2, 7, 83, 2, 2, 3, 83, 2, 2, 5, 89, 2, 2, 89, 3, 2, 2, 3, 5, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(4n+1) = a(4n+2) = 2, for all n >= 0. a(4n) and a(4n+3) are odd primes, for all n >= 0.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

EXAMPLE

a(8) + 9 = 11 + 9 = 20. The smallest prime divisor of 20 is 2. So a(9) = 2.

MATHEMATICA

a = {1}; Do[AppendTo[a, FactorInteger[n + a[[ -1]]][[1, 1]]], {n, 1, 100}]; a (* Stefan Steinerberger, Nov 25 2007 *)

nxt[{n_, a_}]:={n+1, FactorInteger[n+1+a][[1, 1]]}; Transpose[NestList[nxt, {0, 1}, 100]][[2]] (* Harvey P. Dale, Jan 21 2015 *)

CROSSREFS

Cf. A076561.

Sequence in context: A097891 A097611 A135376 * A076561 A132851 A293833

Adjacent sequences:  A132847 A132848 A132849 * A132851 A132852 A132853

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 21 2007

EXTENSIONS

More terms from Stefan Steinerberger, Nov 25 2007

STATUS

approved

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Last modified February 28 11:08 EST 2020. Contains 332323 sequences. (Running on oeis4.)