A072865 Smallest k > 1 dividing tau(k*n) (cf. A000005).

2, 4, 2, 2, 2, 2, 2, 10, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 10, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2

Offset

1,1

Comments

Sequence contains the values 2,3,4,5,6,7,8,9,10,11,12. The smallest x such that a(x)=12 is x = 32768 = 2^15.

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Mathematica

a[n_] := Module[{k = 2}, While[!Divisible[DivisorSigma[0, k*n], k], k++]; k]; Array[a, 100] (* Amiram Eldar, Jun 03 2022 *)

Prog

(PARI) A072865(n) = for(k=2, oo, if(!(numdiv(k*n)%k), return(k))); \\ Antti Karttunen, Sep 27 2018

Crossrefs

Cf. A000005.

Sequence in context: A194564 A284690 A064132 * A364002 A322728 A179686

Adjacent sequences: A072862 A072863 A072864 * A072866 A072867 A072868

Keyword

easy,nonn

Author

Benoit Cloitre, Jul 27 2002

Status

approved