

A046466


Numbers k such that the concatenation of numbers from 1 to k is the product of 7 primes (not necessarily distinct).


1




OFFSET

1,1


LINKS

Table of n, a(n) for n=1..5.
Patrick De Geest, Normal Smarandache Concatenated Numbers, Prime factors from 1 up to n
M. Fleuren, Smarandache Factors and Reverse factors
Carlos Rivera, Primes by Listing, The Prime Puzzles & Problems Connection.


MATHEMATICA

Select[Range[100],
PrimeOmega@FromDigits@Flatten@IntegerDigits@Range@# == 7 &] (* Robert Price, Oct 11 2019 *)


CROSSREFS

Cf. A046460.
Sequence in context: A042621 A042622 A044977 * A054396 A083274 A067913
Adjacent sequences: A046463 A046464 A046465 * A046467 A046468 A046469


KEYWORD

nonn,hard,base


AUTHOR

Patrick De Geest, Aug 15 1998


STATUS

approved



