The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A027989 a(n) = self-convolution of row n of array T given by A027926. 3
 1, 3, 10, 33, 105, 324, 977, 2895, 8462, 24465, 70101, 199368, 563425, 1583643, 4430290, 12342849, 34262337, 94800780, 261545777, 719697255, 1975722326, 5412138033, 14796520365, 40380240528, 110016825025, 299285288499 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) is the number of all columns in stack polyominoes of perimeter 2n+4. - Emanuele Munarini, Apr 07 2011 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 Guo-Niu Han, Enumeration of Standard Puzzles, 2011. [Cached copy] Guo-Niu Han, Enumeration of Standard Puzzles, arXiv:2006.14070 [math.CO], 2020. Index entries for linear recurrences with constant coefficients, signature (6,-11,6,-1). FORMULA a(n) = (2/5)*(n + 1)*F(2*n+3) + (1/5)*F(2*n+2) - (4/5)*(n + 1)*F(2*n), where F(n) = A000045(n). - Ralf Stephan, May 13 2004 From Emanuele Munarini, Apr 07 2011: (Start) a(n) = ((4*n + 5)*F(2*n+1) - (2*n + 1)*F(2*n))/5, where F(n) = A000045(n). a(n) = Sum_{k=0..n} binomial(2*n-k, k)*(k + 1). G.f.: (1 - 3*x + 3*x^2)/(1 - 3*x + x^2)^2. a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) - a(n-4). (End) MATHEMATICA Table[((5+4n)Fibonacci[1+2n]-(1+2n)Fibonacci[2n])/5, {n, 0, 20}] [Emanuele Munarini, Apr 07 2011] PROG (Maxima) makelist(((5+4*n)*fib(1+2*n)-(1+2*n)*fib(2*n))/5, n, 0, 20); [Emanuele Munarini, Apr 07 2011] (PARI) Vec((1-3*x+3*x^2)/(1-3*x+x^2)^2+O(x^66)) /* Joerg Arndt, Apr 08 2011 */ CROSSREFS Cf. A027926, A054142, A172991, A188648. Sequence in context: A062454 A121523 A115240 * A096483 A093043 A061566 Adjacent sequences:  A027986 A027987 A027988 * A027990 A027991 A027992 KEYWORD nonn AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 24 09:01 EST 2022. Contains 350534 sequences. (Running on oeis4.)