# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a187221 Showing 1-1 of 1 %I A187221 #18 Feb 24 2021 02:48:19 %S A187221 0,1,2,4,8,8,8,16,24,16,8,16,24,24,32,56,64,32,8,16,24,24,32,56,64,40, %T A187221 32,56,72,80,120,176,160,64,8,16,24,24,32,56,64,40,32,56,72,80,120, %U A187221 176,160,72,32,56,72,80,120,176,168,112,120,184,224,280,416,512,384,128,8 %N A187221 First differences of A187220. %C A187221 Number of gulls (or G-toothpicks) added at n-th stage to the gullwing structure of A187220. %C A187221 Apparently this is the connection between A147582 and A139251. - Omar E. Pol, Mar 11 2011 %H A187221 David Applegate, The movie version %H A187221 David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.] %H A187221 N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS %F A187221 a(0)=0. a(1)=1. It appears that a(n) = 2*A139251(n-1), for n >= 2. %e A187221 If written as an irregular triangle begins: %e A187221 0, %e A187221 1, %e A187221 2, %e A187221 4, %e A187221 8,8, %e A187221 8,16,24,16, %e A187221 8,16,24,24,32,56,64,32, %e A187221 8,16,24,24,32,56,64,40,32,56,72,80,120,176,160,64, %e A187221 ... %e A187221 Also there is another version in which the layout of the irregular triangle was adjusted to reveal that the columns become constant: %e A187221 .0, %e A187221 .1, %e A187221 .2, %e A187221 .4,8, %e A187221 .8,8,16,24, %e A187221 16,8,16,24,24,32,56,64, %e A187221 32,8,16,24,24,32,56,64,40,32,56,72,80,120,176,160, %e A187221 64,8,16,24,24,32,56,64,40,32,56,72,80,120,176,160,72,32,56,72,80... %Y A187221 Cf. A139250, A139251, A147582, A187211, A187220. %K A187221 nonn %O A187221 0,3 %A A187221 _Omar E. Pol_, Mar 07 2011, Mar 09 2011 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE