The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A107027 Number triangle associated to the Riordan arrays (1/(1+x),x/(1+x)^k),k>=0. 4
 1, 1, 2, 1, 2, 2, 1, 2, 4, 2, 1, 2, 6, 8, 2, 1, 2, 8, 20, 16, 2, 1, 2, 10, 38, 70, 32, 2, 1, 2, 12, 62, 196, 252, 64, 2, 1, 2, 14, 92, 426, 1062, 924, 128, 2, 1, 2, 16, 128, 792, 3112, 5948, 3432, 256, 2, 1, 2, 18, 170, 1326, 7302, 23686, 34120, 12870, 512, 2, 1, 2, 20, 218 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS As a number square read by antidiagonals, the rows represent the row sums of the inverses of the Riordan arrays (1/(1+x),x/(1+x)^k), k>=0. The rows are then given by T(n,k)=(n-1)C(n*k,k)-(n-2)*sum{j=0..k, C(n*k,j)}. T(n,n) is A040000, T(n+1,n) is A000079, T(n+2,n) is A000984, T(n+3,n) is A047098. The reverse of this triangle is A107030. Row sums are A107028. Diagonal sums are A107029. LINKS Table of n, a(n) for n=0..69. FORMULA Number triangle T(n, k)=if(k<=n, (n-k-1)C((n-k)*k, k)-(n-k-2)*sum{j=0..k, C((n-k)*k, j)}, 0). EXAMPLE Triangle begins 1; 1,2; 1,2,2; 1,2,4,2; 1,2,6,8,2; 1,2,8,20,16,2; CROSSREFS Sequence in context: A178522 A131240 A263666 * A355395 A107030 A271362 Adjacent sequences: A107024 A107025 A107026 * A107028 A107029 A107030 KEYWORD easy,nonn,tabl AUTHOR Paul Barry, May 09 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 10 23:37 EST 2023. Contains 367717 sequences. (Running on oeis4.)