%I #8 Jul 19 2024 15:39:46

%S 4,198,31257772,119663504378704719130518,

%T 6713329439711345431716916679280868301022936622514475069583264989008212

%N Number of edge covers in the n-Sierpinski gasket graph.

%H Christian Sievers, <a href="/A356214/b356214.txt">Table of n, a(n) for n = 1..7</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EdgeCover.html">Edge Cover</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SierpinskiGasketGraph.html">Sierpinski Gasket Graph</a>

%o (PARI) a(n)={my(s=[1,0,1,4]);for(k=2,n,s=vector(4,i,sum(xy=1,3,sum(xz=1,3,sum(yz=1,3, s[1+(i>1)+(xy%2)+(xz%2)]*s[1+(i>2)+(xy\2)+(yz%2)]*s[1+(i>3)+(xz\2)+(yz\2)])))));s[4]} \\ _Christian Sievers_, Jul 19 2024

%K nonn

%O 1,1

%A _Eric W. Weisstein_, Jul 29 2022

%E a(4) and beyond from _Christian Sievers_, Jul 19 2024