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 A061667 a(n) = Fibonacci(2*n+1) - 2^(n-1). 14
 1, 3, 9, 26, 73, 201, 546, 1469, 3925, 10434, 27633, 72977, 192322, 506037, 1329885, 3491810, 9161929, 24026745, 62983842, 165055853, 432445861, 1132806018, 2967020769, 7770353441, 20348233858, 53282736741, 139516753581, 365301078434, 956453590585 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Number of cells in the bottom row of all directed column-convex polyominoes of area n+1. Also the binomial transform of A000071 (after removing its 2 leading zeros). - R. J. Mathar, Nov 04 2008 Equals row sums of triangle A147293. - Gary W. Adamson, Nov 05 2008 LINKS Harry J. Smith, Table of n, a(n) for n = 1..200 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. A. Burstein and T. Mansour, Words restricted by 3-letter generalized multipermutation patterns, arXiv:math/0112281 [math.CO], 2001. A. Burstein and T. Mansour, Words restricted by 3-letter generalized multipermutation patterns, Annals. Combin., 7 (2003), 1-14; see Th. 3.8. Index entries for linear recurrences with constant coefficients, signature (5,-7,2). FORMULA G.f.:  x*(1-x)^2/((1-2*x)*(1-3*x+x^2)). - corrected by Philip B. Zhang, Nov 28 2014 a(n) = Sum_{k=0..n+1} C(n+1, k)*sum{j=0..floor(k/2), Fibonacci(k-2j)}. - Paul Barry, Apr 17 2005 a(n) = 2*A001906(n+1)-A001906(n)-A000079(n). - R. J. Mathar, Nov 16 2007 From Colin Barker, Jun 05 2017: (Start) a(n) = 2^(-1-n)*(-5*4^n - (3-sqrt(5))^n*(-5+sqrt(5)) + (3+sqrt(5))^n*(5+sqrt(5))) / 5. a(n) = 5*a(n-1) - 7*a(n-2) + 2*a(n-3) for n>3. (End) MATHEMATICA Table[Fibonacci[2 n + 1] - 2^(n - 1), {n, 1, 100}] (* Vladimir Joseph Stephan Orlovsky, Jul 01 2011 *) PROG (PARI) { for (n=1, 200, write("b061667.txt", n, " ", fibonacci(2*n + 1) - 2^(n - 1))) } \\ Harry J. Smith, Jul 26 2009 (PARI) Vec(x*(1-x)^2/((1-2*x)*(1-3*x+x^2)) + O(x^50)) \\ Michel Marcus, Nov 29 2014 CROSSREFS Cf. A000045. Cf. A147293. - Gary W. Adamson, Nov 05 2008 Sequence in context: A084787 A121190 A054447 * A234270 A258911 A268093 Adjacent sequences:  A061664 A061665 A061666 * A061668 A061669 A061670 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Jun 16 2001 EXTENSIONS Offset changed from 0 to 1 by Harry J. Smith, Jul 26 2009 STATUS approved

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Last modified January 24 13:55 EST 2021. Contains 340409 sequences. (Running on oeis4.)