

A026648


Triangular array T read by rows: T(n,0)=T(n,n)=1 for n >= 0; for n >= 2 and 1<=k<=n1, T(n,k)=T(n1,k1)+T(n2,k1)+T(n1,k) if n is even and k is odd, else T(n,k)=t(n1,k1)+T(n1,k).


15



1, 1, 1, 1, 3, 1, 1, 4, 4, 1, 1, 6, 8, 6, 1, 1, 7, 14, 14, 7, 1, 1, 9, 21, 36, 21, 9, 1, 1, 10, 30, 57, 57, 30, 10, 1, 1, 12, 40, 108, 114, 108, 40, 12, 1, 1, 13, 52, 148, 222, 222, 148, 52, 13, 1, 1, 15, 65, 240, 370, 558, 370, 240, 65, 15, 1, 1, 16
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OFFSET

1,5


LINKS

Table of n, a(n) for n=1..68.


FORMULA

T(n, k) = number of paths from (0, 0) to (nk, k) in the directed graph having vertices (i, j) and edges (i, j)to(i+1, j) and (i, j)to(i, j+1) for i, j >= 0 and edges (i, j)to(i+1, j+1) for i=0, j >= 0 if both i and j are even.
Equals 2*A007318  A034851 (i.e. twice Pascal's triangle  the Losanitch triangle).  Gary W. Adamson, Dec 31 2007


CROSSREFS

Cf. A007318, A034851.
Sequence in context: A238498 A026626 A136482 * A026747 A026374 A174032
Adjacent sequences: A026645 A026646 A026647 * A026649 A026650 A026651


KEYWORD

nonn,tabl


AUTHOR

Clark Kimberling


STATUS

approved



