login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103163 a(n) = gcd(reverse(prime(n)), reverse(prime(n+1))). 1
1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 2, 2, 1, 5, 1, 4, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 14, 2, 2, 2, 4, 2, 2, 8, 2, 2, 2, 4, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 8, 2, 2, 2, 2, 2, 2, 8, 2, 2, 4, 4, 2, 2, 2, 2, 1, 5, 5, 25, 5, 5, 5, 5, 5, 5, 25, 5, 5, 5, 1, 2, 2, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

COMMENTS

Greatest common divisor of two consecutive primes after each prime is written backward.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = gcd(A004087(n), A004087(n+1)).

EXAMPLE

Neither of these common divisors are divisible by 3 or by 10 or by 11.

MAPLE

A103163 := proc(n)

    p := ithprime(n) ;

    q := nextprime(p) ;

    igcd(digrev(p), digrev(q)) ;

end proc:

seq(A103163(n), n=1..114) ; # R. J. Mathar, Sep 22 2018

MATHEMATICA

rd[x_] :=FromDigits[Reversed[IntegerDigits[x]]]; Table[GCD[rd[Prime[w]], rd[Prime[w+1]]], {w, 1, 1000}]

GCD@@#&/@(Partition[IntegerReverse/@Prime[Range[120]], 2, 1]) (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 31 2020 *)

CROSSREFS

Cf. A004087, A000040.

Sequence in context: A336722 A073802 A132157 * A128211 A199393 A010327

Adjacent sequences:  A103160 A103161 A103162 * A103164 A103165 A103166

KEYWORD

base,nonn

AUTHOR

Labos Elemer, Jan 27 2005

EXTENSIONS

Edited by Jon E. Schoenfield, Oct 26 2019

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 9 07:36 EDT 2021. Contains 343692 sequences. (Running on oeis4.)