A320016 a(1) = a(2) = 1; for n > 2, a(n) = A000005(n) * a(A000005(n)), where A000005(n) gives the number of divisors of n.

1, 1, 2, 6, 2, 24, 2, 24, 6, 24, 2, 144, 2, 24, 24, 10, 2, 144, 2, 144, 24, 24, 2, 192, 6, 24, 24, 144, 2, 192, 2, 144, 24, 24, 24, 54, 2, 24, 24, 192, 2, 192, 2, 144, 144, 24, 2, 240, 6, 144, 24, 144, 2, 192, 24, 192, 24, 24, 2, 1728, 2, 24, 144, 14, 24, 192, 2, 144, 24, 192, 2, 1728, 2, 24, 144, 144, 24, 192, 2, 240, 10, 24, 2, 1728

Offset: 1

Author

Antti Karttunen, Nov 24 2018

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10080

Crossrefs

Cf. A000005, A036459, A060937.

Cf. also A320009, A320118.

Programs

GAP

a:=[1,1];; for n in [3..100] do a[n]:=Tau(n)*a[Tau(n)]; od; a; # Muniru A Asiru, Nov 24 2018

Mathematica

Nest[Append[#1, #2 #1[[#2]] ] & @@ {#, DivisorSigma[0, Length@ # + 1]} &, {1, 1}, 82] (* Michael De Vlieger, Nov 25 2018 *)

PARI

A320016(n) = if(n<=2,1,numdiv(n)*A320016(numdiv(n)));

Formula

a(1) = a(2) = 1; for n > 2, a(n) = A000005(n) * a(A000005(n)), where A000005(n) gives the number of divisors of n.