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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A122899 Triangle with row sums counting directed animals. 3
1, 1, 1, 0, 4, 1, 0, 3, 9, 1, 0, 0, 18, 16, 1, 0, 0, 10, 60, 25, 1, 0, 0, 0, 80, 150, 36, 1, 0, 0, 0, 35, 350, 315, 49, 1, 0, 0, 0, 0, 350, 1120, 588, 64, 1, 0, 0, 0, 0, 126, 1890, 2940, 1008 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Row sums are A005773(n+1). Product of A007318 and A122899 is A103371.

LINKS

Table of n, a(n) for n=0..52.

FORMULA

Number triangle T(n,k)=sum{j=0..n, (-1)^(n-j)C(n,j)C(j+1,k+1)C(j,k)}

T(n,k) = C(n,k)*C(k+1,n-k). The columns of this triangle (ignoring leading zeros) give the rows of A123160. - Peter Bala, Jan 24 2008

EXAMPLE

Triangle begins

1,

1, 1,

0, 4, 1,

0, 3, 9, 1,

0, 0, 18, 16, 1,

0, 0, 10, 60, 25, 1,

0, 0, 0, 80, 150, 36, 1,

0, 0, 0, 35, 350, 315, 49, 1,

0, 0, 0, 0, 350, 1120, 588, 64, 1,

0, 0, 0, 0, 126, 1890, 2940, 1008, 81, 1,

0, 0, 0, 0, 0, 1512, 7350, 6720, 1620, 100, 1

CROSSREFS

Cf. A123160.

Sequence in context: A290724 A283879 A216178 * A223856 A153661 A266392

Adjacent sequences:  A122896 A122897 A122898 * A122900 A122901 A122902

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, Sep 18 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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 31 08:50 EDT 2021. Contains 346369 sequences. (Running on oeis4.)