A156821 - OEIS

%I #19 Jun 14 2014 02:30:24

%S 2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,5,5,7,11,13

%N Prime factors of 13! listed with multiplicity.

%e 13! = 2^10 * 3^5 * 5^2 * 7 * 11 * 13.

%e From _Vincenzo Librandi_, Jun 13 2014: (Start)

%e Floor(13/2) = 6, floor(13/4) = 3, floor(13/8) = 1; 6 + 3 + 1 = 10 -> 2^10.

%e Floor(13/3) = 4, floor(13/9) = 1; 4 + 1 = 5 -> 3^5.

%e Floor(13/5) = 2 -> 5^2.

%e Floor(13/7) = 1 -> 7.

%e Floor(13/11) = 1 -> 11.

%e 13/13 = 1 -> 13. (End)

%t Flatten[Table[#[[1]], {#[[2]]}] & /@ FactorInteger[13!]] (* _Alonso del Arte_, Jun 14 2014, based on _Jean-François Alcover_'s program for A027746 *)

%K nonn,fini,full

%O 1,1

%A _Vincenzo Librandi_, Feb 16 2009

%E Edited for clarity by _Jon E. Schoenfield_, Jun 18 2010