A321363 Single-digit odd primes and primes whose decimal expansion has the form iii...ij, where i and j are distinct odd digits.
3, 5, 7, 13, 17, 19, 31, 37, 53, 59, 71, 73, 79, 97, 113, 331, 337, 557, 773, 991, 997, 1117, 3331, 5557, 11113, 11117, 11119, 33331, 77773, 99991, 111119, 333331, 333337, 555557, 3333331, 9999991, 11111117, 11111119, 33333331, 55555553, 55555559, 111111113
Offset: 1
Crossrefs
Programs
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Mathematica
s={3, 5, 7}; Do[Do[Do[k=m*(10^n-1)/9*10+j; If[j!=m && PrimeQ[k], AppendTo[s, k]], {j,1,9,2}], {m,1,9,2}], {n,1,8}]; s (* Amiram Eldar, Nov 08 2018 *) -
PARI
lista(nn) = {print1("3, 5, 7, "); for (n=1, nn, r = (10^n-1)/9; forstep (i=1, 9, 2, forstep(j=1, 9, 2, if (i != j, if (isprime(p=fromdigits(concat(digits(r*i), j))), print1(p, ", "));););););} \\ Michel Marcus, Nov 28 2018
Extensions
a(35)-a(42) from Amiram Eldar, Nov 08 2018
Comments