A107612 Primes with digital product = 2.

2, 211, 2111, 111121, 111211, 112111, 1111211, 1111111121, 1111211111, 1121111111, 111111211111, 111211111111, 2111111111111, 111111111111112111, 111111112111111111, 111111211111111111, 112111111111111111

Offset: 1

Author

Zak Seidov, May 17 2005

Keywords

• base
• nonn

Comments

Corresponding indices of primes in A107611. Cf. A053666, A101987.

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..684

Crossrefs

Cf. A053666, A101987, A107611.

Cf. A004022, A107689, A107690, A107691, A107692, A107693, A107694, A107695, A107696, A107697, A107698.

Programs

Maple

for i from 0 to 30 do it:=sum(10^j, j=0..i): for k from 0 to i do if isprime(it+10^k) then printf(`%d,`, it+10^k) fi: od:od: (Sellers)

Mathematica

Flatten[ Table[ Select[ Sort[ FromDigits /@ Permutations[ Flatten[{2, Table[1, {n}]}]]], PrimeQ[ # ] &], {n, 0, 19}]] (* Robert G. Wilson v, May 19 2005 *)
Select[Flatten[Table[FromDigits/@Permutations[PadRight[{2},n,1]],{n,20}]],PrimeQ]//Sort (* Harvey P. Dale, May 28 2017 *)

Formula

A107612(n) = prime(A107611(n)).

Extensions

More terms from Robert G. Wilson v and James Sellers, May 19 2005