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 A334170 Emirps containing only the digits 1 and 2. 1
 111211, 112111, 12122221, 12222121, 1111122121, 1212211111, 11121211121, 11212221121, 12111212111, 12112221211, 111122221121, 111122222111, 111122222221, 111211221221, 111212212211, 111212222111, 111222212111, 111222221111, 112111211221, 112122112211, 112122211121 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified April 19 10:56 EDT 2024. Contains 371791 sequences. (Running on oeis4.)