0,4

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.

a(2)=1 because f(x1,x2)=x1x2 is equivalent to g(x1,x2)=x1+x2+x1x2 and there are no more monotone Boolean nondegenerate functions of 2 variables.

Sequence in context: A020468 A093946 A001059 this_sequence A132549 A091457 A100906

Adjacent sequences: A120605 A120606 A120607 this_sequence A120609 A120610 A120611

nonn,more

Alan Veliz-Cuba (alanavc(AT)vt.edu), Jun 16 2006