A226778 -id:A226778 - cp's OEIS frontend

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

Erich Friedman, Jun 27 2000

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

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

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

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

Cf. A002113, A004086, A071249, A226778.

a055483 n = gcd n $ a004086 n  -- Reinhard Zumkeller, Jun 18 2013

[Gcd(n, Seqint(Reverse(Intseq(n)))): n in [1..100]]; // Vincenzo Librandi, Oct 29 2014

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

a004086(n)=eval(concat(Vecrev(Str(n))))
a(n)=gcd(n, a004086(n)) \\ Felix Fröhlich, Oct 28 2014

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

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

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

Edited by Robert G. Wilson v, Apr 10 2002

A071249 Numbers k such that gcd(k, R(k)) > 1, where R(k) (A004086) is the digit reversal of k.

Original entry on oeis.org

2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 15, 18, 20, 21, 22, 24, 26, 27, 28, 30, 33, 36, 39, 40, 42, 44, 45, 46, 48, 50, 51, 54, 55, 57, 60, 62, 63, 64, 66, 68, 69, 70, 72, 75, 77, 78, 80, 81, 82, 84, 86, 87, 88, 90, 93, 96, 99, 101, 102, 105, 108, 110, 111, 114, 117, 120, 121

Offset: 1

Amarnath Murthy, May 21 2002

Numbers k such that A055483(k) > 1. - Reinhard Zumkeller, Jun 18 2013

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Cf. A004086, A055483, A226778 (complement).

a071249 n = a071249_list !! (n-1)
a071249_list = filter ((> 1) . a055483) [1..]
-- Reinhard Zumkeller, Jun 18 2013

Select[ Range[125], GCD[ #, FromDigits[ Reverse[ IntegerDigits[ # ]]]] > 1 & ]

Edited by Robert G. Wilson v, Jun 07 2002

Definition corrected by N. J. A. Sloane, Aug 27 2020 following a suggestion from José Hernández Santiago

A337927 a(n) = n / GCD (n, reverse of n).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 10, 1, 4, 13, 14, 5, 16, 17, 2, 19, 10, 7, 1, 23, 4, 25, 13, 3, 14, 29, 10, 31, 32, 1, 34, 35, 4, 37, 38, 13, 10, 41, 7, 43, 1, 5, 23, 47, 4, 49, 10, 17, 52, 53, 6, 1, 56, 19, 58, 59, 10, 61, 31, 7, 32, 65, 1, 67, 34, 23, 10, 71, 8, 73, 74, 25, 76, 1, 26, 79

Offset: 1

Ctibor O. Zizka, Oct 05 2020

a(n)=n for n in A226778. - Robert Israel, Oct 09 2020

			a(12) = 4 since 12 / gcd(12,21) = 4. a(101) = 101 / gcd(101,101) = 1.

Robert Israel, Table of n, a(n) for n = 1..10000

Cf. A000027, A002113, A004086, A055483, A226778.

rev:= proc(n) local L,k;
  L:= convert(n,base,10);
  add(L[-k]*10^(k-1),k=1..nops(L))
end proc:
f:= n -> n/igcd(n,rev(n)):
map(f, [$1..100]); # Robert Israel, Oct 09 2020

Table[n/GCD[n, IntegerReverse[n]], {n, 1, 100}] (* Amiram Eldar, Oct 05 2020 *)

a(n) = n/gcd(n, fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Oct 06 2020

a(n) = n / gcd(n, A004086(n)).
a(n) = n / A055483(n).
a(n) = A000027(n) / A055483(n).

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

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A071249 Numbers k such that gcd(k, R(k)) > 1, where R(k) (A004086) is the digit reversal of k.

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A337927 a(n) = n / GCD (n, reverse of n).

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