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

 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 A348986 A199393 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 20 15:59 EDT 2024. Contains 371844 sequences. (Running on oeis4.)