A321523 List of pairs: primes whose reversal is also prime, each followed by its reversal.

2, 2, 3, 3, 5, 5, 7, 7, 11, 11, 13, 31, 17, 71, 31, 13, 37, 73, 71, 17, 73, 37, 79, 97, 97, 79, 101, 101, 107, 701, 113, 311, 131, 131, 149, 941, 151, 151, 157, 751, 167, 761, 179, 971, 181, 181, 191, 191, 199, 991, 311, 113, 313, 313, 337, 733, 347, 743, 353, 353

Offset

1,1

Links

Table of n, a(n) for n=1..60.

Formula

a(2n-1) = A007500(n).

a(2n) = A004086(A007500(n)).

a(2n) = A095180(n). - Rémy Sigrist, Nov 16 2018

Example

The sequence begins:
     2,  2;
     3,  3;
     5,  5;
     7,  7;
    11, 11;
    13, 31;
    17, 71;
    31, 13;
    37, 73;
    71, 17;
...
107 has its reversal as 701.
971 has its reversal as 179.

Mathematica

Flatten@ Table[ If[PrimeQ[r = IntegerReverse@ p], {p, r}, {}], {p, Prime@ Range@ 71}] (* Giovanni Resta, Nov 13 2018 *)

Prog

(PARI) forprime(p=1, 353, r=fromdigits(Vecrev(digits(p))); if (isprime(r), print1(p ", " r ", "))) \\ Rémy Sigrist, Nov 16 2018

Crossrefs

Subsequence of A135020.

Cf. A000040, A004086, A007500, A095180, A180022.

Sequence in context: A240862 A177716 A109763 * A226748 A119620 A240870

Adjacent sequences: A321520 A321521 A321522 * A321524 A321525 A321526

Keyword

nonn,base,tabf

Author

Kritsada Moomuang, Nov 12 2018

Status

approved