A107120 Numbers n such that pi(n)=prime(d_1*d_2*...*d_k) where d_1 d_2 ... d_k is the decimal expansion of n.

162, 242, 291, 371, 461, 515, 2419, 2815, 11874, 64751, 81927, 264961, 276184, 757155, 2537825, 7717729, 9548491, 14738827, 19728438, 19728446, 19728464, 23695527, 77362954, 269776516, 269776523, 269776532, 358399327, 2385883646, 59955748691, 67893872935, 848472784869

Offset

1,1

Comments

A107121 is a subsequence of this sequence (see the comments line of A107121).

a(32) > 7*10^14, if it exists. - Giovanni Resta, Jun 01 2020

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

Links

Table of n, a(n) for n=1..31.

Example

23695527 is in the sequence because pi(23695527)=prime(2*3*6*9*5*5*2*7).

Mathematica

Do[h = IntegerDigits[m]; l = Length[h]; If[Min[h] > 0 && PrimePi[m] == Prime[Product[h[[k]], {k, l}]], Print[m]], {m, 52000000}]

Crossrefs

Cf. A097223, A107121.

Sequence in context: A045227 A066476 A259220 * A045010 A372972 A373737

Adjacent sequences: A107117 A107118 A107119 * A107121 A107122 A107123

Keyword

nonn,base,fini,changed

Author

Farideh Firoozbakht, May 13 2005

Extensions

a(23)-a(28) from Donovan Johnson, Jul 12 2010

a(29)-a(31) from Giovanni Resta, Jun 01 2020

Status

approved