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

39, 119, 121, 169, 254, 289, 361, 393, 411, 417, 755, 785, 1211, 1253, 1703, 2554, 3503, 3629, 4197, 6401, 7555, 10001, 12131, 12287, 12439, 14803, 15563, 17147, 17363, 23701, 24202, 24322, 24646, 24686, 24746, 25514, 25838, 25918, 25958, 26827, 30383, 30521

Offset

1,1

Links

Paolo P. Lava, Table of n, a(n) for n = 1..100

Example

Aliquot parts of 24332 are 1, 2, 121661; their concatenation in descending order is concat(12166,2,1) = 1216621, which is a palindrome.

Maple

with(numtheory): P:=proc(q) local a, b, c, k, n;
for n from 2 to q do if not isprime(n) then a:=sort([op(divisors(n))]); b:=0;
for k from 1 to nops(a)-1 do b:=b*10^(ilog10(a[k])+1)+a[k]; od; a:=0; c:=b;
for k from 1 to ilog10(b)+1 do a:=10*a+(c mod 10); c:=trunc(c/10); od;
if a=b then print(n); fi; fi; od; end: P(10^9);

Prog

(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

Crossrefs

Cf. A046449.

Sequence in context: A044607 A244694 A008878 * A239562 A044290 A044671

Adjacent sequences: A249298 A249299 A249300 * A249302 A249303 A249304

Keyword

nonn,base

Author

Paolo P. Lava, Oct 24 2014

Status

approved