A046468 Numbers k such that the concatenation of numbers from 1 to k is the product of 9 primes (not necessarily distinct).

26, 36, 40, 52, 74, 90, 102, 112, 114, 115

Offset: 1

Author

Patrick De Geest, Aug 15 1998

Keywords

• nonn
• base
• hard
• more
• less

Links

• Patrick De Geest, Normal Smarandache Concatenated Numbers, Prime factors from 1 up to n
• M. Fleuren, Factors and primes of Smarandache sequences.
• 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[52],PrimeOmega[FromDigits[Flatten[IntegerDigits/@ Range[ #]]]] ==9&] (* Harvey P. Dale, Nov 12 2017 *)

Extensions

a(5)-a(10) from Sean A. Irvine, Apr 10 2021