cp's OEIS Frontend

A354746 Non-repdigit numbers k such that every permutation of the digits of k has the same number of distinct prime divisors.

%I A354746 #18 Jul 23 2022 19:23:55
%S A354746 12,13,15,16,17,21,23,26,28,31,32,36,37,39,45,51,54,56,57,58,61,62,63,
%T A354746 65,68,69,71,73,75,79,82,85,86,93,96,97,113,116,117,122,131,155,156,
%U A354746 161,165,171,177,178,187,199,212,221,224,226,228,242,245,248,254,255,258,262,282
%N A354746 Non-repdigit numbers k such that every permutation of the digits of k has the same number of distinct prime divisors.
%H A354746 Michael S. Branicky, <a href="/A354746/b354746.txt">Table of n, a(n) for n = 1..217</a>
%e A354746 156 is a term because omega(156) = omega(165) = omega (516) = omega(561) = omega(615) = omega(651) = 3, where omega(n) is the number of distinct prime divisors of n.
%t A354746 Select[Range[10000],CountDistinct[PrimeNu[FromDigits /@ Permutations[IntegerDigits[#]]]]==1&&CountDistinct[IntegerDigits[#]]>1&]
%o A354746 (Python)
%o A354746 from sympy import factorint
%o A354746 from itertools import permutations
%o A354746 def ok(n):
%o A354746     s, pf = str(n), len(factorint(n))
%o A354746     if len(set(s)) == 1: return False
%o A354746     return all(pf==len(factorint(int("".join(p)))) for p in permutations(s))
%o A354746 print([k for k in range(500) if ok(k)]) # _Michael S. Branicky_, Jun 05 2022
%Y A354746 Cf. A001221, A003459, A115662, A354745.
%K A354746 nonn,base
%O A354746 1,1
%A A354746 _Metin Sariyar_, Jun 05 2022