

A259846


Number of steps to get from n to 1 by process of replacing with sum of divisors if the result is odd, or dividing by 2 if even.


0



0, 1, 3, 2, 5, 4, 4, 3, 7, 6, 6, 5, 6, 5, 7, 4, 9, 8, 8, 7, 6, 7, 7, 6, 7, 7, 9, 6, 9, 8, 6, 5, 8, 10, 8, 9, 10, 9, 8, 8, 8, 7, 9, 8, 10, 8, 8, 7, 11, 8, 11, 8, 11, 10, 11, 7, 10, 10, 10, 9, 8, 7, 10, 6, 9, 9, 12, 11, 9, 9, 11, 10, 12, 11, 9, 10, 9, 9, 10, 9
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OFFSET

1,3


LINKS

Table of n, a(n) for n=1..80.


EXAMPLE

a(9)= 7 because 9 > sigma(9)= 13 > sigma(13)= 14 > 7 > sigma(7)= 8 > 4 > 2 > 1, hence the trajectory {9 > 13 > 14 > 7 > 8 > 4 > 2 > 1} with 7 iterations.


MATHEMATICA

f[n_]:=Module[{a=n, k=0}, While[a!=1, k++; If[EvenQ[a], a=a/2, a=DivisorSigma[1, a]]]; k]; Table[f[n], {n, 1, 150}]


CROSSREFS

Cf. A000203.
Sequence in context: A140061 A292776 A061313 * A087669 A053087 A316519
Adjacent sequences: A259843 A259844 A259845 * A259847 A259848 A259849


KEYWORD

nonn,easy


AUTHOR

Michel Lagneau, Jul 07 2015


STATUS

approved



