login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A055483 a(n) is the GCD of n and the reverse of n. 21
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 (list; graph; refs; listen; history; text; internal format)
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.
Sequence in context: A047813 A084051 A069652 * A331472 A364362 A059717
KEYWORD
base,easy,nonn,nice,changed
AUTHOR
Erich Friedman, Jun 27 2000
EXTENSIONS
Edited by Robert G. Wilson v, Apr 10 2002
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 2 08:43 EST 2024. Contains 370461 sequences. (Running on oeis4.)