A046463 Numbers k such that the concatenation of numbers from 1 to k is the product of 4 primes (not necessarily distinct).

9, 16, 23, 29, 37, 38, 43, 58, 59

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Patrick De Geest, Normal Smarandache Concatenated Numbers, Prime factors from 1 up to n

M. Fleuren, Factors and primes of Smarandache sequences.

Carlos Rivera, Primes by Listing, The Prime Puzzles & Problems Connection.

Mathematica

Select[Range[60], PrimeOmega[FromDigits[Flatten[IntegerDigits/@ Range[#]]]] == 4&] (* Harvey P. Dale, Jan 15 2013 *)

Crossrefs

Cf. A046460.

Sequence in context: A287186 A134256 A199859 * A003332 A345793 A091571

Adjacent sequences: A046460 A046461 A046462 * A046464 A046465 A046466

Keyword

nonn,hard,base

Author

Patrick De Geest, Aug 15 1998

Status

approved