A334170 Emirps containing only the digits 1 and 2.

111211, 112111, 12122221, 12222121, 1111122121, 1212211111, 11121211121, 11212221121, 12111212111, 12112221211, 111122221121, 111122222111, 111122222221, 111211221221, 111212212211, 111212222111, 111222212111, 111222221111, 112111211221, 112122112211, 112122211121

Offset

1,1

Links

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Mathematica

Union @ Flatten @ Table[FromDigits /@ Select[Tuples[{1, 2}, n] , PrimeQ @ (m = FromDigits[#]) && # != (r = Reverse[#]) && PrimeQ @ FromDigits[r] &], {n, 12}] (* Amiram Eldar, Apr 18 2020 *)
Table[Select[FromDigits/@Tuples[{1, 2}, n], !PalindromeQ[#]&&AllTrue[ {#, IntegerReverse[ #]}, PrimeQ]&], {n, 12}]//Flatten (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Nov 08 2020 *)

Prog

(PARI) isok(p) = if (isprime(p), my(d=digits(p), rd=Vecrev(d)); (vecsort(d, , 8) == [1, 2]) && isprime(fromdigits(rd)) && (rd != d));
lista(nn) = {for (n=1, nn, my(vf = vector(n, k, 1)); for (i=1, 2^n-1, my(vpos = select(x->(x==1), Vecrev(binary(i)), 1), nvf = vf); for (i=1, #vpos, nvf[vpos[i]] = 2; ); my(x = eval(Str(1, fromdigits(Vecrev(nvf)), 1))); if (isok(x), print1(x, ", ")); ); ); } \\ Michel Marcus, Apr 18 2020

Crossrefs

Intersection of A007931 and A006567.

Subsequence of A020450.

Sequence in context: A109716 A292471 A228253 * A179919 A296370 A206509

Adjacent sequences: A334167 A334168 A334169 * A334171 A334172 A334173

Keyword

nonn,base

Author

Daniel Starodubtsev, Apr 17 2020

Status

approved