|
| |
|
|
A105450
|
|
Binomial(n+5,6) + binomial(n+3,3) + binomial(n+2,3) + binomial(n-1,1).
|
|
4
| |
|
|
0, 6, 22, 60, 142, 305, 607, 1134, 2008, 3396, 5520, 8668, 13206, 19591, 28385, 40270, 56064, 76738, 103434, 137484, 180430, 234045, 300355, 381662, 480568, 600000, 743236, 913932, 1116150, 1354387, 1633605, 1959262, 2337344, 2774398, 3277566, 3854620
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
COMMENTS
| Number of directed column-convex polyominoes with perimeter 2(n+4) having n cells in the foundational column.
A051743 and this sequence form successive diagonals in an array that has as row sums the sequence A006027.
|
|
|
FORMULA
| a(0)=0, a(1)=6, a(2)=22, a(3)=60, a(4)=142, a(5)=305, a(6)= 607, a(n)=7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)- 7*a(n-6)+a(n-7) [From Harvey P. Dale, June 28 2011]
G.f.: (2*x^6-11*x^5+26*x^4-32*x^3+20*x^2-6*x)/(x-1)^7 [From Harvey P. Dale, June 28 2011]
|
|
|
MATHEMATICA
| Table[Binomial[n+5, 6]+Binomial[n+3, 3]+Binomial[n+2, 3]+ Binomial[n-1, 1], {n, 0, 50}] (* or *) LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {0, 6, 22, 60, 142, 305, 607}, 51] (* From Harvey P. Dale, June 28 2011 *)
|
|
|
CROSSREFS
| Cf. A051743, A006027, A051743.
Sequence in context: A127760 A066188 A071239 * A011888 A081282 A001769
Adjacent sequences: A105447 A105448 A105449 * A105451 A105452 A105453
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Douglas G. Rogers (douglas(AT)mi.uib.no), May 07 2005
|
| |
|
|
