A124511 a(n) = A124508(A124508(n)).

1, 36, 36, 72, 36, 144, 36, 144, 72, 144, 36, 288, 36, 144, 144, 288, 36, 288, 36, 288, 144, 144, 36, 576, 72, 144, 144, 288, 36, 576, 36, 576, 144, 144, 144, 576, 36, 144, 144, 576, 36, 576, 36, 288, 288, 144, 36, 1152, 72, 288, 144, 288, 36, 576, 144, 576, 144

Offset: 1

Author

Reinhard Zumkeller, Nov 04 2006

Keywords

• nonn
• easy

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Reinhard Zumkeller)

Crossrefs

Cf. A001221, A001222, A003586, A124508, A124512.

Programs

Mathematica

a[n_] := 9 * 2^(PrimeNu[n] + PrimeOmega[n]); a[1] = 1; Array[a, 100] (* Amiram Eldar, Jul 11 2023 *)

PARI

a(n) = my(f = factor(n)); if(n == 1, 1, 9 * 2^(omega(f) + bigomega(f))); \\ Amiram Eldar, Jul 11 2023

Formula

a(n) = A124512(n) / 4 for n > 1.

A124512(n) = A124508(a(n)).

For primes p, q with p <> q: a(p) = 36; a(p*q) = 144; a(p^k) = 9*2^(k+1) = 6*A124508(n), k > 0.

a(n) = 9 * 2^(omega(n) + Omgea(n)) = 9 * 2^(A001221(n) + A001222(n)), for n >= 2. - Amiram Eldar, Jul 11 2023