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 A220521 Number of toothpicks or D-toothpicks added at n-th stage in the toothpick structure of A220520. 12
 1, 2, 4, 4, 4, 4, 8, 8, 4, 4, 8, 12, 16, 12, 16, 16, 4, 4, 8, 12, 16, 20, 24, 26, 24, 12, 20, 32, 40, 28, 32, 32, 4, 4, 8, 12, 16, 20, 24, 26, 24, 20, 32, 44, 64, 52, 48, 54, 40, 12, 20, 36, 48, 56, 64, 74, 76, 30, 44, 72, 88, 60, 64, 64, 4, 4, 8, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS From Omar E. Pol, Apr 26 2020: (Start) The cellular automaton described in A220520 has word "ab", so the structure of this triangle is as follows: a,b; a,b; a,b,a,b; a,b,a,b,a,b,a,b; a,b,a,b,a,b,a,b,a,b,a,b,a,b,a,b; ... The row lengths are the terms of A011782 multiplied by 2, equaling the column 2 of the square array A296612: 2, 2, 4, 8, 16, ... This arrangement has the property that the odd-indexed columns (a) contain numbers of the toothpicks of length 1, and the even-indexed columns (b) contain numbers of the D-toothpicks. For further information about the "word" of a cellular automaton see A296612. (End) LINKS N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS EXAMPLE Written as an irregular triangle the sequence begins: 1,2; 4,4; 4,4,8,8; 4,4,8,12,16,12,16,16; 4,4,8,12,16,20,24,26,24,12,20,32,40,28,32,32; 4,4,8,12,16,20,24,26,24,20,32,44,64,52,48,54,40,12,20,... Triangle reformatted by Omar E. Pol, Apr 26 2020 CROSSREFS First differences of A220520. First differs from A194441 at a(14). Columns 1-3: A123932, A040002, A010731. Cf. A139250, A139251, A194443, A220501, A220523, A296612. Sequence in context: A235863 A220495 A194441 * A236680 A162798 A088650 Adjacent sequences:  A220518 A220519 A220520 * A220522 A220523 A220524 KEYWORD nonn,tabf AUTHOR Omar E. Pol, Dec 15 2012 EXTENSIONS 0 removed and offset changed by Omar E. Pol, Apr 26 2020 STATUS approved

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Last modified November 25 17:30 EST 2020. Contains 338625 sequences. (Running on oeis4.)