A109308 Lesser emirps (primes whose digit reversal is a larger prime).

13, 17, 37, 79, 107, 113, 149, 157, 167, 179, 199, 337, 347, 359, 389, 709, 739, 769, 1009, 1021, 1031, 1033, 1061, 1069, 1091, 1097, 1103, 1109, 1151, 1153, 1181, 1193, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1279, 1283, 1381, 1399, 1409, 1429

Offset

1,1

Links

R. J. Mathar, Table of n, a(n) for n = 1..1000

Maple

read("transforms"):
A109308 := proc(n)
    option remember;
    local p, R ;
    if n = 1 then
        return 13 ;
    else
        p := nextprime(procname(n-1)) ;
        while true do
            R := digrev(p) ;
            if R> p and isprime(R) then
                return p;
            end if;
            p := nextprime(p) ;
        end do:
    end if;
end proc: # R. J. Mathar, Oct 12 2012

Mathematica

dr[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Prime[Range[1000]], PrimeQ[dr[ # ]]&&dr[ # ]>#&]

Prog

(PARI) isok(p) = if (isprime(p), my(q=fromdigits(Vecrev(digits(p)))); (p < q) && isprime(q)); \\ Michel Marcus, Sep 07 2021
(Python)
from sympy import isprime, primerange
def ok(p): revp = int(str(p)[::-1]); return p < revp and isprime(revp)
print(list(filter(ok, primerange(1, 1430)))) # Michael S. Branicky, Sep 07 2021

Crossrefs

Cf. A006567 (emirps), A109309 (larger emirps).

Sequence in context: A307894 A322472 A166681 * A263241 A246944 A086402

Adjacent sequences: A109305 A109306 A109307 * A109309 A109310 A109311

Keyword

base,nonn

Author

Zak Seidov, Jun 25 2005

Status

approved