A050676 Let b(n) = number of prime factors (with multiplicity) of concatenation of numbers from 1 to n; sequence gives smallest number m with b(m) = n.

1, 3, 2, 9, 8, 11, 28, 6, 26, 20

Offset: 1

Author

Patrick De Geest, Aug 15 1999

Keywords

• nonn
• base
• hard
• more

Comments

a(11) <= 148, a(12) = 104, a(13) = 100, a(14) = 54, a(15) <= 184. - Michael S. Branicky, Dec 14 2022 using factorizations at the De Geest link

Links

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

Crossrefs

Cf. A007908, A050678, A046460.

Programs

Mathematica

Join[{1},Table[i=1; While[PrimeOmega[FromDigits[Flatten[IntegerDigits[Range[i]]]]]!=n,i++]; i,{n,2,10}]] (* Jayanta Basu, May 30 2013 *)