OFFSET
0,3
COMMENTS
Two Boolean functions belong to the same big equivalence class (bec) when they can be expressed by each other by negating and permuting arguments. E.g., when f(~p,r,q) = g(p,q,r), then f and g belong to the same bec. Geometrically this means that the functions correspond to hypercubes with binarily colored vertices that are equivalent up to rotation and reflection.
Boolean functions correspond to integers, so each bec can be denoted by the smallest integer corresponding to one of its functions. There are A000616(n) big equivalence classes of n-ary Boolean functions. Ordered by size they form the finite sequence A_n. It is the beginning of A_(n+1), which leads to this infinite sequence A.
LINKS
Tilman Piesk, Table of n, a(n) for n = 0..9999
Tilman Piesk, Big equivalence classes of Boolean functions
Tilman Piesk, bec of 4-ary functions corresponding to a(85) = 854 = 0x0356
Tilman Piesk, MATLAB code used for the calculation
EXAMPLE
The 16 2-ary functions ordered in A000616(2) = 6 big equivalence classes:
a a(n) Boolean functions hypercube (square)
0 0 0000 empty
1 1 0001, 0010, 0100, 1000 one in a corner
2 3 0011, 1100, 0101, 1010 ones on a side
3 6 0110, 1001 ones on a diagonal
4 7 0111, 1011, 1101, 1110 ones in 3 corners
5 15 1111 full
CROSSREFS
KEYWORD
nonn
AUTHOR
Tilman Piesk, Jul 22 2013
STATUS
approved