OFFSET
1,1
COMMENTS
a(6) has 108 decimal digits.
LINKS
Christian Sievers, Table of n, a(n) for n = 1..8 (1..6 from Andrew Howroyd)
Eric Weisstein's World of Mathematics, Dominating Set
Eric Weisstein's World of Mathematics, Sierpinski Sieve Graph
PROG
(PARI) a(n)={my(s=[[1, 0, 0, 0], [0, 0, 1], [0, 1], [1]]); 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)])))))); [1, 3, 3, 1]*vectorv(4, i, s[i][5-i])} \\ Christian Sievers, Jul 21 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Sep 04 2021
EXTENSIONS
Terms a(4) and beyond from Andrew Howroyd, Jan 19 2022
STATUS
approved