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

1,3

Links

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

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.

Mathematica

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

Prog

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

Crossrefs

Cf. A000005, A036459, A060937.

Cf. also A320009, A320118.

Sequence in context: A008556 A254638 A320118 * A096485 A125032 A076743

Adjacent sequences: A320013 A320014 A320015 * A320017 A320018 A320019

Keyword

nonn

Author

Antti Karttunen, Nov 24 2018

Status

approved