OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Keller Graph
Eric Weisstein's World of Mathematics, Maximal Independent Vertex Set
Eric Weisstein's World of Mathematics, Minimal Vertex Cover
PROG
(Python)
from itertools import zip_longest
from sympy.ntheory.factor_ import digits
from networkx import empty_graph, find_cliques
def A290607(n):
k = 1<<(n<<1)
G = empty_graph(range(k))
G.add_edges_from((a, b) for a in range(k) for b in range(a) if (s:=tuple(c-d&3 for c, d in zip_longest(digits(a, 4)[-1:0:-1], digits(b, 4)[-1:0:-1], fillvalue=0))).count(2)==0 or s.count(0)>len(s)-2)
return sum(1 for c in find_cliques(G)) # Chai Wah Wu, Jan 11 2024
KEYWORD
nonn,more
AUTHOR
Eric W. Weisstein, Aug 07 2017
EXTENSIONS
a(5) from Eric W. Weisstein, Nov 05 2018
a(6) from Chai Wah Wu, Jan 11 2024
STATUS
approved