A046467 Numbers k such that the concatenation of numbers from 1 to k is the product of 8 primes (not necessarily distinct).

6, 21, 27, 35, 48, 53, 60, 62, 66, 92, 106, 108, 117

Offset: 1

Author

Patrick De Geest, Aug 15 1998

Keywords

• nonn
• base
• hard
• more

Links

• Patrick De Geest, Normal Smarandache Concatenated Numbers, Prime factors from 1 up to n
• M. Fleuren, Smarandache Factors and Reverse factors
• Carlos Rivera, Puzzle 8. Primes by Listing, The Prime Puzzles & Problems Connection.

Crossrefs

Cf. A046460.

Programs

Mathematica

Select[Range[100], PrimeOmega@FromDigits@Flatten@IntegerDigits@Range@# == 8 &] (* Robert Price, Oct 11 2019 *)

Extensions

a(9)-a(13) from Sean A. Irvine, Apr 10 2021