A176558 a(n) is the reverse concatenation of divisors of n.

1, 21, 31, 421, 51, 6321, 71, 8421, 931, 10521, 111, 1264321, 131, 14721, 15531, 168421, 171, 1896321, 191, 20105421, 21731, 221121, 231, 2412864321, 2551, 261321, 27931, 28147421, 291, 30151065321, 311, 32168421, 331131, 341721, 35751, 361812964321, 371

Offset: 1

Author

Jaroslav Krizek, Apr 20 2010

Keywords

• nonn
• base

Comments

Union of A089374(n) for n >= 1 and A175354(n) for n >= 2. - Jonathan Vos Post, Apr 17 2011

Examples

			For n=12; divisors of 12: 1,2,3,4,6,12; a(12)=1264321 (reverse concatenation).
		

Links

• Indranil Ghosh, Table of n, a(n) for n = 1..50000

Crossrefs

Cf. A089374, A175354, A175355, A176588, A176589.

Programs

Maple

a:= n-> parse(cat(sort([numtheory[divisors](n)[]], `>`)[])):
seq(a(n), n=0..40);  # Alois P. Heinz, Dec 31 2020

Mathematica

Table[FromDigits@ Flatten@ Map[IntegerDigits, Reverse@ Divisors@ n], {n, 34}] (* Michael De Vlieger, Jan 23 2017 *)

PARI

a(n) = {s = ""; fordiv(n, d, s = concat(Str(d), s)); eval(s);} \\ Michel Marcus, Feb 16 2015

Python

from sympy import divisors
def a(n): return int("".join(str(d) for d in divisors(n)[::-1]))
print([a(n) for n in range(1, 35)]) # Michael S. Branicky, Dec 31 2020

Extensions

More terms from Charles R Greathouse IV, Apr 23 2010

Corrected by Jaroslav Krizek, Apr 26 2010

Edited by Charles R Greathouse IV, Apr 30 2010