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

1,1

Links

Table of n, a(n) for n=1..42.

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 *)

Prog

(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

Crossrefs

Cf. A051200, A055558, A062353, A065582, A105975, A141311, A320256.

Sequence in context: A327819 A045398 A162565 * A355853 A155045 A144296

Adjacent sequences: A321360 A321361 A321362 * A321364 A321365 A321366

Keyword

nonn,base

Author

Enrique Navarrete, Nov 07 2018

Extensions

a(35)-a(42) from Amiram Eldar, Nov 08 2018

Status

approved