cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

Original entry on oeis.org

461, 264961, 9548491, 14738827
Offset: 1

Views

Author

Farideh Firoozbakht, May 13 2005

Keywords

Comments

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

Examples

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

Crossrefs

Cf. A097223, A107120, A107122.

Programs

  • 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}]
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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