A292968 - OEIS

%I #30 Feb 16 2025 08:33:51

%S 4,27,10054,499058851840,60978122299433248924629725740007424,

%T 111234802292550535463100810323266662685051007497410845234355027801887222800563874025554401906714958888960

%N Number of matchings in the n-Sierpinski sieve graph.

%H Christian Sievers, <a href="/A292968/b292968.txt">Table of n, a(n) for n = 1..8</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IndependentEdgeSet.html">Independent Edge Set</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Matching.html">Matching</a>

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

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

%K nonn

%O 1,1

%A _Eric W. Weisstein_, Sep 30 2017

%E a(5) and beyond from _Christian Sievers_, Jul 19 2024