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 A261711 Triangle read by rows: T(n,k) is the number of words over alphabet {0,1,2,3} having exactly k occurrences of the string 01, where n>=0 and k>=0. 1
 1, 4, 15, 1, 56, 8, 209, 46, 1, 780, 232, 12, 2911, 1091, 93, 1, 10864, 4912, 592, 16, 40545, 21468, 3366, 156, 1, 151316, 91824, 17784, 1200, 20, 564719, 386373, 89238, 8010, 235, 1, 2107560, 1604984, 430992, 48624, 2120, 24, 7865521, 6598282, 2021103, 275724, 16255, 330, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Rows n = 0..200, flattened Rigoberto Flórez, Leandro Junes, José L. Ramírez, Further Results on Paths in an n-Dimensional Cubic Lattice, Journal of Integer Sequences, Vol. 21 (2018), Article 18.1.2. Ran Pan, Problem 5, Project P. FORMULA G.f.: 1/(1-4*x-(y-1)*x^2). EXAMPLE 1 4 15 1 56 8 209 46 1 780 232 12 2911 1091 93 1 10864 4912 592 16 40545 21468 3366 156 1 151316 91824 17784 8010 20 MAPLE b:= proc(n, t) option remember; expand(`if`(n=0, 1,       add(b(n-1, i)*`if`(t=1 and i=2, x, 1), i=1..4)))     end: T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n, 0)): seq(T(n), n=0..12);  # Alois P. Heinz, Aug 29 2015 CROSSREFS Column k=0 is A001353(n+1). The triangle is shifted from A207823. Sequence in context: A097548 A218047 A127910 * A128235 A024547 A328839 Adjacent sequences:  A261708 A261709 A261710 * A261712 A261713 A261714 KEYWORD easy,nonn,tabf AUTHOR Ran Pan, Aug 29 2015 STATUS approved

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Last modified May 28 04:00 EDT 2020. Contains 334671 sequences. (Running on oeis4.)