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 A211964 Right triangle from the snowflake (or E-toothpick) structure of A161330 (see Comments lines for definition). 2
 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, 80, 82, 86, 90, 95, 103, 109, 120, 128, 136, 145, 151, 158, 166, 174, 182, 187, 193, 203, 210, 221, 232, 241, 250, 262, 271, 285, 294, 304, 318, 329, 343, 353, 362, 371 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS 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. LINKS N. J. A. Sloane, A single E-toothpick N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS FORMULA a(n) = (((A161330(n+1) - 2)/6) + n)/2. a(n) = A220478(n)/2. - Omar E. Pol, Feb 19 2012 CROSSREFS Cf. A139250, A161328, A161330, A213360, A213366, A211976, A220478. Sequence in context: A224955 A006856 A249013 * A140199 A072190 A177445 Adjacent sequences:  A211961 A211962 A211963 * A211965 A211966 A211967 KEYWORD nonn AUTHOR Omar E. Pol, Dec 17 2012 STATUS approved

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Last modified December 3 05:05 EST 2021. Contains 349445 sequences. (Running on oeis4.)