cp's OEIS Frontend

A306474 Composite numbers that are anagrams of the concatenation of their prime factors.

%I A306474 #15 May 20 2020 16:28:11
%S A306474 735,1255,3792,7236,11913,12955,13175,17276,17482,19075,19276,23535,
%T A306474 25105,32104,34112,37359,42175,100255,101299,104392,105295,107329,
%U A306474 117067,117873,121325,121904,121932,123544,123678,124483,127417,129595,131832,132565,139925
%N A306474 Composite numbers that are anagrams of the concatenation of their prime factors.
%C A306474 The sequence contains two subsequences:
%C A306474 Subsequence 1: numbers with distinct digits. This finite subsequence begins with the numbers 735, 3792, 7236, 17482, 19075, 19276, 32104, ...
%C A306474 Subsequence 2: numbers with non-distinct digits. This subsequence begins with the numbers 1255, 11913, 12955, 13175, 17276, 23535, ...
%H A306474 Robert Israel, <a href="/A306474/b306474.txt">Table of n, a(n) for n = 1..500</a>
%e A306474 3792 is in the sequence because the concatenation of the prime distinct divisors {2, 3, 79} is 2379, anagram of 3792.
%p A306474 with(numtheory):
%p A306474 for n from 1 to 140000 do:
%p A306474 if type(n,prime)=false
%p A306474   then
%p A306474   x:=factorset(n):n1:=nops(x): s:=0:s0:=0:
%p A306474     for i from n1 by -1 to 1 do:
%p A306474      a:=x[i]:b:=length(a):s:=s+a*10^s0:s0:=s0+b:
%p A306474     od:
%p A306474       if sort(convert(n, base, 10)) = sort(convert(s, base, 10))
%p A306474        then
%p A306474         printf(`%d, `, n):
%p A306474         else
%p A306474       fi:fi:
%p A306474      od:
%t A306474 Select[Range[2,140000],If [!PrimeQ[#],Sort@IntegerDigits@#==Sort[Join@@IntegerDigits[First/@FactorInteger[#]]]]&]
%Y A306474 Cf. A023086, A209799.
%Y A306474 A121342 is a subsequence.
%K A306474 nonn,base
%O A306474 1,1
%A A306474 _Michel Lagneau_, Feb 18 2019