A000612 Number of P-equivalence classes of switching functions of n or fewer variables, divided by 2. (Formerly M1712 N0677)

1, 2, 6, 40, 1992, 18666624, 12813206169137152, 33758171486592987164087845043830784, 1435913805026242504952006868879460423834904914948818373264705576411070464

Offset

0,2

Comments

Also number of nonisomorphic sets of nonempty subsets of an n-set.

Equivalently, number of nonisomorphic fillings of a Venn diagram of n sets. - Joerg Arndt, Mar 24 2020

Number of hypergraphs on n unlabeled nodes. - Charles R Greathouse IV, Apr 06 2021

References

M. A. Harrison, Introduction to Switching and Automata Theory. McGraw Hill, NY, 1965, p. 153.

S. Muroga, Threshold Logic and Its Applications. Wiley, NY, 1971, p. 38 Table 2.3.2. - Row 5.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Alois P. Heinz, Table of n, a(n) for n = 0..12

M. A. Harrison, The number of equivalence classes of Boolean functions under groups containing negation, IEEE Trans. Electron. Comput. 12 (1963), 559-561.

M. A. Harrison, The number of equivalence classes of Boolean functions under groups containing negation, IEEE Trans. Electron. Comput. 12 (1963), 559-561. [Annotated scanned copy]

Geon Lee, Seokbum Yoon, Jihoon Ko, Hyunju Kim, and Kijung Shin, Hypergraph Motifs and Their Extensions Beyond Binary, arXiv:2310.15668 [cs.SI], 2023.

Wikipedia, Venn diagram

Index entries for sequences related to Boolean functions

Formula

a(n) = A003180(n)/2.

Example

Non-isomorphic representatives of the a(2) = 6 set-systems are 0, {1}, {12}, {1}{2}, {1}{12}, {1}{2}{12}. - Gus Wiseman, Aug 07 2018

Maple

a:= n-> add(1/(p-> mul((c-> j^c*c!)(coeff(p, x, j)), j=1..degree(p)))(
        add(x^i, i=l))*2^((w-> add(mul(2^igcd(t, l[i]), i=1..nops(l)),
        t=1..w)/w)(ilcm(l[]))), l=combinat[partition](n))/2:
seq(a(n), n=0..9);  # Alois P. Heinz, Aug 12 2019

Mathematica

sysnorm[{}] := {}; sysnorm[m_]:=If[Union@@m!=Range[Max@@Flatten[m]], sysnorm[m/.Rule@@@Table[{(Union@@m)[[i]], i}, {i, Length[Union@@m]}]], First[Sort[sysnorm[m, 1]]]]; sysnorm[m_, aft_]:=If[Length[Union@@m]<=aft, {m}, With[{mx=Table[Count[m, i, {2}], {i, Select[Union@@m, #>=aft&]}]}, Union@@(sysnorm[#, aft+1]&/@Union[Table[Map[Sort, m/.{par+aft-1->aft, aft->par+aft-1}, {0, 1}], {par, First/@Position[mx, Max[mx]]}]])]];
Table[Length[Union[sysnorm/@Subsets[Rest[Subsets[Range[n]]]]]], {n, 4}] (* Gus Wiseman, Aug 07 2018 *)
a[n_] := Sum[1/Function[p, Product[Function[c, j^c*c!][Coefficient[p, x, j]], {j, 1, Exponent[p, x]}]][Total[x^l]]*2^(Function[w, Sum[Product[2^GCD[t, l[[i]]], {i, 1, Length[l]}], {t, 1, w}]/w][If[l=={}, 1, LCM @@ l]]), {l, IntegerPartitions[n]}]/2;
a /@ Range[0, 9] (* Jean-François Alcover, Feb 04 2020, after Alois P. Heinz *)

Crossrefs

a(n) = A003180(n)/2.

Cf. A007716, A055621, A058891, A283877, A300913, A306005, A317533, A317757.

Sequence in context: A337699 A051185 A118623 * A319633 A367365 A367603

Adjacent sequences: A000609 A000610 A000611 * A000613 A000614 A000615

Keyword

nonn,easy,nice,core

Author

N. J. A. Sloane

Extensions

More terms from Vladeta Jovovic, Feb 23 2000

Status

approved