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%I #21 Feb 21 2013 15:43:28
%S 0,1,2,3,5,6,8,10,12,15,17,20,24,25,27,29,32,37,40,47,51,56,63,67,73,
%T 80,82,86,90,95,103,109,120,128,136,145,151,158,166,174,182,187,193,
%U 203,210,221,232,241,250,262,271,285,294,304,318,329,343,353,362,371
%N Right triangle from the snowflake (or E-toothpick) structure of A161330 (see Comments lines for definition).
%C If n >> 1 the structure looks like a right triangle, which is essentially half of one of the six wedges of the E-toothpick (or snowflake) structure of A161330. The sequence gives the number of E-toothpicks in the structure after n stages. A211976 (the first differences) gives the number added at the n-th stage.
%H N. J. A. Sloane, <a href="/A161330/a161330.jpg">A single E-toothpick</a>
%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>
%H <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a>
%F a(n) = (((A161330(n+1) - 2)/6) + n)/2.
%F a(n) = A220478(n)/2. - _Omar E. Pol_, Feb 19 2012
%Y Cf. A139250, A161328, A161330, A213360, A213366, A211976, A220478.
%K nonn
%O 0,3
%A _Omar E. Pol_, Dec 17 2012
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