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%I #21 Apr 10 2021 16:59:34
%S 28,30,42,44,46,69,72,82,84,86,93,109,116
%N Numbers k such that the concatenation of numbers from 1 to k is the product of 7 primes (not necessarily distinct).
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/factorlist.htm">Normal Smarandache Concatenated Numbers, Prime factors from 1 up to n</a>
%H M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/micha.txt">Smarandache Factors and Reverse factors</a>
%H Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles & Problems Connection.
%t Select[Range[100], PrimeOmega@FromDigits@Flatten@IntegerDigits@Range@# == 7 &] (* _Robert Price_, Oct 11 2019 *)
%Y Cf. A046460.
%K nonn,base,hard,more
%O 1,1
%A _Patrick De Geest_, Aug 15 1998
%E a(6)-a(13) from _Sean A. Irvine_, Apr 10 2021
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