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 A121299 Sum of the heights of all directed column-convex polyominoes of area n; here by the height of a polyomino one means the number of lines of slope -1 that pass through the centers of the polyomino cells). 2
 1, 4, 14, 47, 149, 458, 1373, 4046, 11765, 33857, 96611, 273760, 771164, 2161352, 6031104, 16764719, 46442640, 128268379, 353296944, 970717966, 2661204271, 7280832780, 19882745230, 54203791062, 147536291969, 400991600305 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS E. Barcucci, A. Del Lungo, R. Pinzani and R. Sprugnoli, La hauteur des polyominos dirigés verticalement convexes, Actes du 31e Séminaire Lotharingien de Combinatoire, Publi. IRMA, Université Strasbourg I (1993). E. Barcucci, R. Pinzani and R. Sprugnoli, Directed column-convex polyominoes by recurrence relations, Lecture Notes in Computer Science, No. 668, Springer, Berlin (1993), pp. 282-298. FORMULA a(n) = Sum(k*A121298(n,k), k=1..n). [Corrected by R. J. Mathar, Sep 18 2007] EXAMPLE a(2)=4 because the vertical and the horizontal dominoes have altogether 4 diagonals with slope -1. MAPLE T:=proc(n, k) if n<=0 or k<=0 then 0 elif n=1 and k=1 then 1 else T(n-1, k-1)+add(T(n-k, j), j=1..k-1)+add(T(n-j, k-1), j=1..k-1) fi end: seq(add(k*T(n, k), k=1..n), n=1..15); CROSSREFS Cf. A121298. Sequence in context: A258255 A124805 A121530 * A326346 A046718 A291385 Adjacent sequences:  A121296 A121297 A121298 * A121300 A121301 A121302 KEYWORD nonn AUTHOR Emeric Deutsch, Aug 04 2006 EXTENSIONS More terms from R. J. Mathar, Sep 18 2007 STATUS approved

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Last modified June 22 10:56 EDT 2021. Contains 345375 sequences. (Running on oeis4.)