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

%I A109308 #17 Sep 08 2021 19:17:03
%S A109308 13,17,37,79,107,113,149,157,167,179,199,337,347,359,389,709,739,769,
%T A109308 1009,1021,1031,1033,1061,1069,1091,1097,1103,1109,1151,1153,1181,
%U A109308 1193,1213,1217,1223,1229,1231,1237,1249,1259,1279,1283,1381,1399,1409,1429
%N A109308 Lesser emirps (primes whose digit reversal is a larger prime).
%H A109308 R. J. Mathar, <a href="/A109308/b109308.txt">Table of n, a(n) for n = 1..1000</a>
%p A109308 read("transforms"):
%p A109308 A109308 := proc(n)
%p A109308     option remember;
%p A109308     local p,R ;
%p A109308     if n = 1 then
%p A109308         return 13 ;
%p A109308     else
%p A109308         p := nextprime(procname(n-1)) ;
%p A109308         while true do
%p A109308             R := digrev(p) ;
%p A109308             if R> p and isprime(R) then
%p A109308                 return p;
%p A109308             end if;
%p A109308             p := nextprime(p) ;
%p A109308         end do:
%p A109308     end if;
%p A109308 end proc: # _R. J. Mathar_, Oct 12 2012
%t A109308 dr[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Select[Prime[Range[1000]], PrimeQ[dr[ # ]]&&dr[ # ]>#&]
%o A109308 (PARI) isok(p) = if (isprime(p), my(q=fromdigits(Vecrev(digits(p)))); (p < q) && isprime(q)); \\ _Michel Marcus_, Sep 07 2021
%o A109308 (Python)
%o A109308 from sympy import isprime, primerange
%o A109308 def ok(p): revp = int(str(p)[::-1]); return p < revp and isprime(revp)
%o A109308 print(list(filter(ok, primerange(1, 1430)))) # _Michael S. Branicky_, Sep 07 2021
%Y A109308 Cf. A006567 (emirps), A109309 (larger emirps).
%K A109308 base,nonn
%O A109308 1,1
%A A109308 _Zak Seidov_, Jun 25 2005