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A199881 Triangle T(n,k), read by rows, given by (1,-1,0,0,0,0,0,0,0,0,0,...) DELTA (1,0,-1,1,0,0,0,0,0,0,0,...) where DELTA is the operator defined in A084938. 0
1, 1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 0, 2, 3, 1, 0, 0, 1, 4, 4, 1, 0, 0, 0, 3, 7, 5, 1, 0, 0, 0, 1, 7, 11, 6, 1, 0, 0, 0, 0, 4, 14, 16, 7, 1, 0, 0, 0, 0, 1, 11, 25, 22, 8, 1, 0, 0, 0, 0, 0, 5, 25, 41, 29, 9, 1, 0, 0, 0, 0, 0, 1, 16, 50, 63, 37, 10, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,9

COMMENTS

A skewed version of triangular array A072405.

LINKS

Table of n, a(n) for n=0..77.

FORMULA

T(n,k)=T(n-1,k-1)+T(n-2,k-1) starting with T(0,0)=T(1,0)=T(1,1)=T(2,1)=T(2,2)=1 and T(2,0)=0.

G.f.: (1+x-y*x^2)/(1-y*x-y*x^2).

T(2n,n)=A028310(n).

EXAMPLE

Triangle begins :

1

1, 1

0, 1, 1

0, 1, 2, 1 (key row for starting the recurrence)

0, 0, 2, 3, 1

0, 0, 1, 4, 4, 1

0, 0, 0, 3, 7, 5, 1

0, 0, 0, 1, 7, 11, 6, 1

0, 0, 0, 0, 4, 14, 16, 7, 1

CROSSREFS

Cf. A000931 (diagonal sums), A042950(column sums), A055389 (row sums)

Sequence in context: A120730 A122851 A064301 * A060701 A275345 A259668

Adjacent sequences:  A199878 A199879 A199880 * A199882 A199883 A199884

KEYWORD

nonn,tabl

AUTHOR

Philippe Deléham, Nov 11 2011

STATUS

approved

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Last modified October 19 14:21 EDT 2018. Contains 316362 sequences. (Running on oeis4.)