A337925 Digits of n rearranged to be the smallest number with the fewest possible prime factors, counted with multiplicity. Terms retain the same number of digits as n, i.e. leading digits may not be zero.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 21, 13, 41, 15, 61, 17, 18, 19, 20, 21, 22, 23, 42, 25, 26, 27, 82, 29, 30, 13, 23, 33, 43, 53, 63, 37, 83, 39, 40, 41, 42, 43, 44, 45, 46, 47, 84, 49, 50, 15, 25, 53, 45, 55, 65, 57, 58, 59, 60, 61, 26, 63, 46, 65, 66, 67, 86, 69, 70, 17, 27, 37, 47, 57, 67, 77

Offset: 1

Author

Roderick Kimball, Sep 30 2020

Keywords

• nonn
• look
• base

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001222, A004186, A328447.

Programs

Mathematica

a[n_] := Module[{p = FromDigits /@ Select[Permutations @ IntegerDigits[n], First[#] > 0 &]}, o = PrimeOmega[p]; Min[p[[Position[o, Min[o]] // Flatten]]]]; Array[a, 100] (* Amiram Eldar, Oct 19 2020 *)

PARI

a(n) = {my(d = digits(n), v = select(x->#(digits(x))==#d, vector((#d)!, i, fromdigits(vector(#d, k, d[numtoperm(#d, i-1)[k]])))), b = vecmin(vector(#v, k, bigomega(v[k])))); vecmin(select(x->(bigomega(x)==b), v));} \\ Michel Marcus, Oct 19 2020

Formula

a(a(n)) = a(n). - Rémy Sigrist, Oct 22 2020