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 A220498 Number of E-toothpicks (or tridents) added at n-th stage to the structure of the equilateral triangle of A220478. 3
 0, 2, 2, 2, 4, 2, 4, 4, 4, 6, 4, 6, 8, 2, 4, 4, 6, 10, 6, 14, 8, 10, 14, 8, 12, 14, 4, 8, 8, 10, 16, 12, 22, 16, 16, 18, 12, 14, 16, 16, 16, 10, 12, 20, 14, 22, 22, 18, 18, 24, 18, 28, 18, 20, 28, 22, 28, 20, 18, 18, 22, 32, 32, 26, 24, 22, 28, 28, 32, 34, 20, 20, 28 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Essentially the first differences of A220478. REFERENCES Mohammad K. Azarian, A Trigonometric Characterization of  Equilateral Triangle, Problem 336, Mathematics and Computer Education, Vol. 31, No. 1, Winter 1997, p. 96.  Solution published in Vol. 32, No. 1, Winter 1998, pp. 84-85. Mohammad K. Azarian, Equating Distances and Altitude in an Equilateral Triangle, Problem 316, Mathematics and Computer Education, Vol. 28, No. 3, Fall 1994, p. 337.  Solution published in Vol. 29, No. 3, Fall 1995, pp. 324-325. LINKS N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS FORMULA a(n) = 1 + A161331(n+1)/6 = 2*A211976(n). CROSSREFS Cf. A139250, A139251, A160121, A161330, A161329, A161331, A211974, A211976. Sequence in context: A005137 A222959 A309441 * A105681 A240039 A130127 Adjacent sequences:  A220495 A220496 A220497 * A220499 A220500 A220501 KEYWORD nonn AUTHOR Omar E. Pol, Feb 19 2013 STATUS approved

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Last modified September 16 12:40 EDT 2019. Contains 327112 sequences. (Running on oeis4.)