A120618 - OEIS

%I #2 May 11 2007 03:00:00

%S 1,2,4,12,90,3831

%N Number of inequivalent (under "inversion of variables") monotone Boolean functions of n or fewer variables.

%C We define the "inversion of variables", i, by (i.f)(x1,...,xn)=1+f(1+x1,...,1+xn). Note that {i,identity function} is a group. It turns out that if f is a monotone function, then i.f is also a monotone function. f is equivalent to g if f=g or f=i.g.

%e a(1)=2 because m(x)=0,n(x)=1,k(x)=x are the three monotone Boolean functions (of 1 or fewer variables) and m,n are equivalent.

%Y Cf. A120608, A120587, A006602.

%K nonn,more

%O 0,2

%A Alan Veliz-Cuba (alanavc(AT)vt.edu), Jun 18 2006