cp's OEIS Frontend

A249301 Composite numbers whose concatenation of their aliquot parts, in descending order, is a palindrome.

%I A249301 #12 Oct 26 2014 17:32:45
%S A249301 39,119,121,169,254,289,361,393,411,417,755,785,1211,1253,1703,2554,
%T A249301 3503,3629,4197,6401,7555,10001,12131,12287,12439,14803,15563,17147,
%U A249301 17363,23701,24202,24322,24646,24686,24746,25514,25838,25918,25958,26827,30383,30521
%N A249301 Composite numbers whose concatenation of their aliquot parts, in descending order, is a palindrome.
%H A249301 Paolo P. Lava, <a href="/A249301/b249301.txt">Table of n, a(n) for n = 1..100</a>
%e A249301 Aliquot parts of 24332 are 1, 2, 121661; their concatenation in descending order is concat(12166,2,1) = 1216621, which is a palindrome.
%p A249301 with(numtheory): P:=proc(q) local a,b,c,k,n;
%p A249301 for n from 2 to q do if not isprime(n) then a:=sort([op(divisors(n))]); b:=0;
%p A249301 for k from 1 to nops(a)-1 do b:=b*10^(ilog10(a[k])+1)+a[k]; od; a:=0; c:=b;
%p A249301 for k from 1 to ilog10(b)+1 do a:=10*a+(c mod 10); c:=trunc(c/10); od;
%p A249301 if a=b then print(n); fi; fi; od; end: P(10^9);
%o A249301 (PARI) isok(n) = {d = vecsort(divisors(n),,4); if (#d > 2, s = ""; for (i=2, #d, s = concat(s, Str(d[i]));); d = digits(eval(s)); d == Vecrev(d););} \\ _Michel Marcus_, Oct 25 2014
%Y A249301 Cf. A046449.
%K A249301 nonn,base
%O A249301 1,1
%A A249301 _Paolo P. Lava_, Oct 24 2014