0,2

At 0, the last variable, the only choice is (t, f) because the first entry is always uncomplemented and the 2nd must be different.

At level 1, the 2nd to last variable, the first entry is either t or a pointer to a following level (0) and the 2nd entry is either of these or its negation, except it may not equal the first entry.

At level n, the n-th to last variable, the first entry is either t or a pointer to one of the following levels' functions and the second entry is any of these or its negation, but not equal to the first entry

David L. Dill, BDD's

Author?, More about BDD's

a(n) = (S(n-1) + 1) * (2*S(n-1) + 1) where S(n-1) = sum k<n a(k).

a(n) is the (2^(2^n)-1)-th triangular number; i.e. a(n) = 2^(2^n)*(2^(2^n)-1)/2.

(PARI) a(n)=if(n<=0, n==0, 2^(2^n)*(2^(2^n)-1)/2)

Sequence in context: A053777 A023199 A007539 this_sequence A110442 A137149 A053710

Adjacent sequences: A040993 A040994 A040995 this_sequence A040997 A040998 A040999

nonn

R. H. Hardin (rhhardin(AT)att.net)