This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A121633 Sum of the bottom levels of the last column over all deco polyominoes of height n. A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column. 4
 0, 0, 1, 9, 68, 527, 4408, 40303, 403046, 4393339, 51955528, 663383135, 9102982354, 133668773755, 2092209897524, 34783032728383, 612234346270510, 11375905660965179, 222544581264066400, 4572536725690159999, 98456173247669999978, 2217126753620449439515 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS a(n) = Sum(k*A121632(n,k), k>=0). REFERENCES E. Barcucci, A. Del Lungo and R. Pinzani, "Deco" polyominoes, permutations and random generation, Theoretical Computer Science, 159, 1996, 29-42. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..449 FORMULA a(1)=0; a(n) = n*a(n-1)+(n-1)!-1 for n>=2. a(n)= A000254(n)- A002672(n) a(n)= n!*sum(1/k,k=1..10)- floor(n!(e-1)) [From Gary Detlefs, Jul 18 2010] EXAMPLE a(2)=0 because the deco polyominoes of height 2 are the vertical and horizontal dominoes, all of whose columns start at level 0. MAPLE a[1]:=0: for n from 2 to 23 do a[n]:=n*a[n-1]+(n-1)!-1 od: seq(a[n], n=1..23); MATHEMATICA RecurrenceTable[{a[1]==0, a[n]==n*a[n-1]+(n-1)!-1}, a, {n, 20}] (* Harvey P. Dale, Dec 01 2013 *) CROSSREFS Cf. A121632, A000254. Sequence in context: A133120 A194650 A048742 * A091708 A024119 A120306 Adjacent sequences:  A121630 A121631 A121632 * A121634 A121635 A121636 KEYWORD nonn AUTHOR Emeric Deutsch, Aug 12 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 August 22 17:52 EDT 2019. Contains 326182 sequences. (Running on oeis4.)