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
Examples
31 - 13 = 18, 71 - 17 = 54, 73 - 37 = 36 (distance between lesser emirps and their reversals).
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
- Carlos Rivera, Puzzle 20. Reversible Primes, The Prime Puzzles and Problems Connection.
Programs
-
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 *)
-
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
Extensions
Better name and more terms from Jon E. Schoenfield, Aug 20 2021