The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A121753 Number of deco polyominoes of height n in which all columns end at an odd level. A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column. 2
 1, 1, 2, 6, 16, 62, 230, 1114, 5268, 30702, 176226, 1201638, 8107464, 63339702, 491010102, 4324845834, 37867131900, 371275954758, 3623124865986, 39137296073094, 421150512316032, 4969568447400366, 58455531552960198 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n)=A121698(n,0). REFERENCES E. Barcucci, S. Brunetti and F. Del Ristoro, Succession rules and deco polyominoes, Theoret. Informatics Appl., 34, 2000, 1-14. E. Barcucci, A. Del Lungo and R. Pinzani, "Deco" polyominoes, permutations and random generation, Theoretical Computer Science, 159, 1996, 29-42. LINKS FORMULA Recurrence relation: a(n)=(1+2floor((n-2)/2))a(n-1)-[floor((n-1)/2)floor((n-2)/2)-1]a(n-2) for n>=3, a(1)=1, a(2)=1. EXAMPLE a(2)=1 because the deco polyominoes of height 2 are the vertical and horizontal dominoes and only the horizontal one has all of its columns ending at an odd level. MAPLE a[1]:=1: a[2]:=1: for n from 3 to 26 do a[n]:= (1+2*floor((n-2)/2))*a[n-1]-(floor((n-1)/2)*floor((n-2)/2)-1)*a[n-2] od: seq(a[n], n=1..26); CROSSREFS Cf. A121698, A121751. Sequence in context: A093113 A150030 A150031 * A173994 A150032 A283420 Adjacent sequences:  A121750 A121751 A121752 * A121754 A121755 A121756 KEYWORD nonn AUTHOR Emeric Deutsch, Aug 23 2006 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 December 6 18:16 EST 2021. Contains 349567 sequences. (Running on oeis4.)