%I #6 Feb 24 2021 02:48:19
%S 1,1,4,13,4,13,43,25,4,13,43,25,43,142,118,37,4,13,43,25,43,142,118,
%T 37,43,142,118,154,469,496,229,49,4,13,43,25,43,142,118,37,43,142,118,
%U 154,469,496,229,49,43,142,118,154,469,496,229,166,469,496,580,1561,1957,1183
%N a(0) = 1, a(1) = 1; a(2^i + j) = a(j) + 3a(j + 1) for 0 <= j < 2^i.
%H David Applegate, Omar E. Pol and N. J. A. Sloane, <a href="/A000695/a000695_1.pdf">The Toothpick Sequence and Other Sequences from Cellular Automata</a>, Congressus Numerantium, Vol. 206 (2010), 157191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n1)1) for n >= 2.]
%H N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a>
%K nonn
%O 0,3
%A _N. J. A. Sloane_, Jan 02 2010
