OFFSET
1,1
LINKS
Christian Sievers, Table of n, a(n) for n = 1..9
Eric Weisstein's World of Mathematics, Minimum Dominating Set
Eric Weisstein's World of Mathematics, Sierpinski Sieve Graph
PROG
(PARI) a(n)={my(s=[[1+O(x), 0, 0, 0], [0, 0, x+O(x^2)], [0, x^2+O(x^3)], [x^3+O(x^4)]]); for(k=2, n, s=vector(4, i, vector(5-i, j, sum(xy=0, 3, sum(xz=0, 3, sum(yz=0, 3, s[1+(i>1)+!xy+!xz][1+(j>3)+(xy%2)+(xz%2)]*s[1+(i>2)+!xy+!yz][1+(j>2)+(xy\2)+(yz%2)]*s[1+(i>3)+!xz+!yz][1+(j>1)+(xz\2)+(yz\2)]/x^(!xy+!xz+!yz))))))); pollead([1, 3, 3, 1]*vectorv(4, i, s[i][5-i]))} \\ Christian Sievers, Jul 21 2024, improved Jul 25 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Jan 28 2019
EXTENSIONS
a(5) and beyond from Christian Sievers, Jul 21 2024
STATUS
approved