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

1,2

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

Table of n, a(n) for n=1..10.

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.

Mathematica

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

Crossrefs

Cf. A007908, A050678, A046460.

Sequence in context: A201926 A288055 A081233 * A356185 A010372 A199455

Adjacent sequences: A050673 A050674 A050675 * A050677 A050678 A050679

Keyword

nonn,base,hard,more

Author

Patrick De Geest, Aug 15 1999

Status

approved