A053212 Number of divisors of the minimal numbers (A007416).

1, 2, 3, 4, 6, 5, 8, 9, 10, 12, 7, 16, 15, 18, 14, 20, 24, 21, 30, 32, 27, 28, 11, 36, 25, 40, 48, 42, 22, 45, 13, 60, 35, 54, 50, 56, 64, 33, 72, 26, 63, 80, 44, 84, 90, 70, 96, 75, 39, 81, 100, 66, 49, 108, 120, 112, 52, 17, 55, 128, 126, 88, 144, 105, 160

Offset: 1

Author

Asher Auel, Dec 16 1999

Keywords

• nonn
• nice

Comments

A permutation of the natural numbers.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
• Index entries for sequences that are permutations of the natural numbers.

Crossrefs

Cf. A000005, A007416, A005179.

Inverse permutation to A064787.

Programs

Haskell

a053212 = a000005' . a007416  -- Reinhard Zumkeller, Apr 18 2015

Mathematica

Reap[For[n = 1, n <= 10^5, n++, tau = DivisorSigma[0, n]; If[Abs[Product[DivisorSigma[0, k] - tau, {k, 1, n - 1}]] > 0, Print[tau]; Sow[tau]]]][[2, 1]] (* Jean-François Alcover, Jan 16 2013 *)

Formula

a(n) = A000005(A007416(n)). - Omar E. Pol, Dec 26 2008

Extensions

More terms from Naohiro Nomoto, Apr 03 2001