%I A048631
%S A048631 1,1,2,6,24,120,272,1904,15232,124800,848640,7507200,39738368,
%T A048631 433441792,2589116416,30419859456,486717751296,8128101580800,
%U A048631 132557598294016,1971862458400768,30421253686034432,512675443057623040
%N A048631 Xfactorials - like factorials but use carryless GF(2)[ X ] polynomial 
               multiplication.
%C A048631 In formula X stands for the multiplication in a ring of GF(2)[ X ] polynomials
%F A048631 a(0) = 1, a(n) = n X a(n-1) (See the Maple function Xfactorial given 
               below).
%p A048631 Xfactorial := proc(n); if(0 = n) then RETURN(1); else RETURN(Xmult(n,
               Xfactorial(n-1))); fi; end;
%p A048631 Xmult := proc(n,m) option remember; if(0 = n) then RETURN(0); else RETURN(XORnos(((n 
               mod 2)*m),Xmult(floor(n/2),m*2))); fi; end;
%Y A048631 Cf. A000142, A048720, A048632, A061922.
%Y A048631 Sequence in context: A066616 A083267 A130480 this_sequence A062348 A072856 
               A070946
%Y A048631 Adjacent sequences: A048628 A048629 A048630 this_sequence A048632 A048633 
               A048634
%K A048631 easy,nonn
%O A048631 0,3
%A A048631 Antti Karttunen