A119791 a(1) = 1, a(n) = number of divisors of n*a(n-1).

1, 2, 4, 5, 3, 6, 8, 7, 6, 12, 12, 15, 8, 10, 12, 14, 8, 15, 8, 12, 18, 18, 12, 18, 18, 18, 12, 20, 12, 24, 16, 10, 16, 12, 24, 24, 16, 12, 18, 30, 16, 24, 16, 14, 24, 20, 12, 21, 8, 15, 12, 20, 12, 20, 18, 30, 24, 20, 12, 30, 16, 12, 24, 20, 18, 24, 16, 14, 16, 24, 16, 24, 16, 12

Offset

1,2

Comments

a(n)=A000005(n*a(n-1)) for n>1, a(1)=1;

see A119792 and A119793 for record values and where they occur: A119792(n)=a(A119793(n)).

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Mathematica

Fold[Append[#1, DivisorSigma[0, #1[[-1]]*#2]] &, {1}, Range[2, 74]] (* Ivan Neretin, Sep 01 2016 *)
nxt[{n_, a_}]:={n+1, DivisorSigma[0, a(n+1)]}; NestList[nxt, {1, 1}, 80][[;; , 2]] (* Harvey P. Dale, Nov 16 2024 *)

Crossrefs

Sequence in context: A065182 A060120 A065183 * A317687 A026257 A357986

Adjacent sequences: A119788 A119789 A119790 * A119792 A119793 A119794

Keyword

nonn

Author

Reinhard Zumkeller, May 24 2006

Status

approved