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A072268 a(0)=1; a(n+1) = 1 + f(a(n))^2, where f(x) is the largest prime factor of x (A006530). 6
1, 2, 5, 26, 170, 290, 842, 177242, 160802, 2810, 78962, 9223370, 5033760602, 2935496262242, 2154284576409188208716642, 1379590379356276893461978662419832989306970202, 10320758390549056348725939119133160378521185060950774444682 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Is the sequence bounded?

Essentially the same as A031439; a(n) = A031439(n-1)^2 + 1. - Charles R Greathouse IV, May 08 2009

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

Given a(5)=290: a(6) = 1 + lpf(a(5))^2 = 1 + lpf(290)^2 = 1 + 29^2 = 842.

MAPLE

with(numtheory): a[0]:=1: a[1]:=2: for n from 2 to 20 do b:=factorset(a[n-1]): a[n]:=1+op(nops(b), b)^2: od: seq(a[n], n=0..20); # Emeric Deutsch, Feb 05 2006

CROSSREFS

Cf. A031439.

Sequence in context: A120762 A226170 A334639 * A019014 A128595 A180749

Adjacent sequences:  A072265 A072266 A072267 * A072269 A072270 A072271

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 08 2002

EXTENSIONS

More terms from Emeric Deutsch, Feb 05 2006

a(16) corrected by T. D. Noe, Nov 26 2007

STATUS

approved

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Last modified October 19 15:34 EDT 2021. Contains 348091 sequences. (Running on oeis4.)