A346756 Lesser emirps (A109308) subtracted from their reversals.

18, 54, 36, 18, 594, 198, 792, 594, 594, 792, 792, 396, 396, 594, 594, 198, 198, 198, 7992, 180, 270, 2268, 540, 8532, 810, 6804, 1908, 7902, 360, 2358, 630, 2718, 1908, 5904, 1998, 7992, 90, 6084, 8172, 8262, 8442, 2538, 450, 8532, 7632, 7812, 7902, 2088, 270

Offset

1,1

Links

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

Carlos Rivera, Puzzle 20. Reversible Primes, The Prime Puzzles and Problems Connection.

Formula

a(n) = reverse(A109308(n)) - A109308(n).

Example

31 - 13 = 18, 71 - 17 = 54, 73 - 37 = 36 (distance between lesser emirps and their reversals).

Maple

rev:= proc(n) local L, i;
  L:= convert(n, base, 10);
  add(L[-i]*10^(i-1), i=1..nops(L));
end proc:
f:= proc(p) local r;
  if not isprime(p) then return NULL fi;
  r:= rev(p);
  if r > p and isprime(r) then r-p else NULL fi
end proc:
map(f, [seq(i, i=11 .. 10^4, 2)]); # Robert Israel, Dec 28 2023

Mathematica

f[n_] := IntegerReverse[n] - n; Map[f, Select[Range[1500], f[#] > 0 && PrimeQ[#] && PrimeQ @ IntegerReverse[#] &]] (* Amiram Eldar, Sep 08 2021 *)

Prog

(PARI) rev(p) = fromdigits(Vecrev(digits(p))); \\ A004086
lista(nn) = {my(list = List()); forprime (p=1, nn, my(q=rev(p)); if ((q>p) && isprime(q), listput(list, q-p)); ); Vec(list); } \\ Michel Marcus, Sep 07 2021
(Python)
from sympy import isprime, nextprime
def aupton(terms):
    alst, p = [], 2
    while len(alst) < terms:
        revp = int(str(p)[::-1])
        if p < revp and isprime(revp):
            alst.append(revp - p)
        p = nextprime(p)
    return alst
print(aupton(49)) # Michael S. Branicky, Sep 08 2021

Crossrefs

Cf. A004086, A006567, A109308.

Sequence in context: A052902 A217591 A059137 * A096011 A176026 A068396

Adjacent sequences: A346753 A346754 A346755 * A346757 A346758 A346759

Keyword

nonn,base,look

Author

George Bull, Aug 20 2021

Extensions

Better name and more terms from Jon E. Schoenfield, Aug 20 2021

Status

approved