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A249300 Composite numbers whose concatenation of their aliquot parts, in ascending order, is a palindrome. 1
93, 121, 393, 497, 755, 842, 961, 993, 1042, 1255, 1293, 1642, 1681, 1893, 1897, 3721, 3755, 3997, 4043, 4061, 4442, 5041, 5755, 6797, 8197, 8842, 9993, 11042, 11255, 16593, 17309, 17642, 22255, 23221, 23597, 26242, 26493, 26797, 29793, 30043, 30242, 30383 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
Aliquot parts of 157442 are 1, 2, 78621; their concatenation in ascending order is concat(1,2,78621) = 1278621, 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 nops(a)-1 by -1 to 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)); if (#d > 2, s = ""; for (i=1, #d-1, s = concat(s, Str(d[i])); ); d = digits(eval(s)); d == Vecrev(d); ); } \\ Michel Marcus, Oct 25 2014
CROSSREFS
Cf. A046449.
Sequence in context: A167776 A099019 A082131 * A153684 A048257 A255991
KEYWORD
nonn,base
AUTHOR
Paolo P. Lava, Oct 24 2014
STATUS
approved

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Last modified April 23 07:34 EDT 2024. Contains 371905 sequences. (Running on oeis4.)