A174900 a(n) = the smallest numbers k such that A007955(k) = n, or 0 if there is no such k, where A007955(m) = product of divisors of m.

1, 2, 3, 0, 5, 0, 7, 4, 0, 0, 11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 0, 0, 23, 0, 0, 0, 9, 0, 29, 0, 31, 0, 0, 0, 0, 6, 37, 0, 0, 0, 41, 0, 43, 0, 0, 0, 47, 0, 0, 0, 0, 0, 53, 0, 0, 0, 0, 0, 59, 0, 61, 0, 0, 8, 0, 0, 67, 0, 0, 0, 71, 0, 73, 0, 0, 0, 0, 0, 79, 0, 0, 0, 83

Offset: 1

Author

Jaroslav Krizek, Apr 01 2010

Keywords

• nonn

Comments

a(n) = the largest numbers k such that A007955 (k) = n, or 0 if there is no such k.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007955.

Programs

Mathematica

With[{m = 100}, s[n_] := n^(DivisorSigma[0, n]/2); (FirstPosition[Array[s, m], #] & /@ Range[m]) /. Missing["NotFound"] -> 0 // Flatten] (* Amiram Eldar, Aug 06 2024 *)

Extensions

More terms from Amiram Eldar, Aug 06 2024