A107121 Numbers n such that n=prime(prime(d_1*d_2*...*d_k)) where d_1 d_2 ... d_k is the decimal expansion of n.

461, 264961, 9548491, 14738827

Offset

1,1

Comments

If n is in the sequence then pi(n) = prime(d_1*d_2*...*d_k) where d_1 d_2 ... d_k is the decimal expansion of n, so this sequence is a subsequence of A107120.

The sequence is finite as n >= 10^(k-1) grows faster than prime(prime(9^k)) >= prime(prime(d_1*d_2*...*d_k)). If it exists, a(5) > 10^14. - Max Alekseyev, Dec 30 2024

Links

Table of n, a(n) for n=1..4.

Example

14738827 is in the sequence because 14738827=prime(prime(1*4*7*3*8*8*2*7)).

Mathematica

Do[h= IntegerDigits[Prime[m]]; l = Length[h]; If[Min[h] > 0 && m == Prime[Product[h[[k]], {k, l}]], Print[Prime [m]]], {m, 20000000}]

Crossrefs

Cf. A097223, A107120, A107122.

Sequence in context: A142832 A277989 A138956 * A101734 A059025 A267200

Adjacent sequences: A107118 A107119 A107120 * A107122 A107123 A107124

Keyword

base,fini,nonn,more,changed

Author

Farideh Firoozbakht, May 13 2005

Status

approved