A055483 a(n) is the GCD of n and the reverse of n.

1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 11, 3, 1, 1, 3, 1, 1, 9, 1, 2, 3, 22, 1, 6, 1, 2, 9, 2, 1, 3, 1, 1, 33, 1, 1, 9, 1, 1, 3, 4, 1, 6, 1, 44, 9, 2, 1, 12, 1, 5, 3, 1, 1, 9, 55, 1, 3, 1, 1, 6, 1, 2, 9, 2, 1, 66, 1, 2, 3, 7, 1, 9, 1, 1, 3, 1, 77, 3, 1, 8, 9, 2, 1, 12, 1, 2, 3, 88, 1, 9, 1, 1, 3, 1, 1, 3, 1, 1, 99, 1, 101, 3, 1, 1, 3, 1, 1, 9, 1, 11, 111

Offset

1,2

Comments

a(A226778(n)) = 1; a(A071249(n)) > 1. - Reinhard Zumkeller, Jun 18 2013

a(n) = n iff n >= 1 is a palindrome (n is in A002113). - Felix Fröhlich, Oct 28 2014

Links

Indranil Ghosh, Table of n, a(n) for n = 1..50000 (first 1000 terms from T. D. Noe)

Formula

a(n) = gcd(n, A004086(n)). - Felix Fröhlich, Oct 28 2014

3 | a(n) if 3 | n and 9 | a(n) if 9 | n. - Alonso del Arte, Aug 31 2021

Example

a(12) = 3 since gcd(12, 21) = 3.
a(13) = 1 since 13 and 31 are coprime.
a(101) = gcd(101, 101) = 101.

Mathematica

gcn[n_] := GCD[n, IntegerReverse[n]]; Array[gcn, 120] (* Harvey P. Dale, Jan 23 2012 *)

Prog

(Haskell)
a055483 n = gcd n $ a004086 n  -- Reinhard Zumkeller, Jun 18 2013
(PARI) a004086(n)=eval(concat(Vecrev(Str(n))))
a(n)=gcd(n, a004086(n)) \\ Felix Fröhlich, Oct 28 2014
(Magma) [Gcd(n, Seqint(Reverse(Intseq(n)))): n in [1..100]]; // Vincenzo Librandi, Oct 29 2014
(Scala) def reverseDigits(n: Int): Int = Integer.parseInt(n.toString.reverse)
def euclGCD(a: Int, b: Int): Int = b match { case 0 => a; case n => Math.abs(euclGCD(b, a % b)) }
(1 to 120).map(n => euclGCD(n, reverseDigits(n))) // Alonso del Arte, Aug 31 2021
(Python)
from math import gcd
def a(n): return gcd(n, int(str(n)[::-1]))
print([a(n) for n in range(1, 112)]) # Michael S. Branicky, Aug 31 2021

Crossrefs

Different from A069652, first differs at a(101), since gcd(101, 110) = 1.

Cf. A002113, A004086, A071249, A226778.

Sequence in context: A047813 A084051 A069652 * A331472 A364362 A059717

Adjacent sequences: A055480 A055481 A055482 * A055484 A055485 A055486

Keyword

base,easy,nonn,nice

Author

Erich Friedman, Jun 27 2000

Extensions

Edited by Robert G. Wilson v, Apr 10 2002

Status

approved