login
This site is supported by donations to The OEIS Foundation.

 

Logo

Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A118032 Triangle T, read by rows, such that diagonal 2n of T equals diagonal n of T^2 and diagonal 2n+1 of T equals diagonal n of T*U: [T^2](n,k) = T(2n-k,k) and [T*U](n,k) = T(2n+1-k,k) for n>=k, k>=0, where U = SHIFT_UP(T). 17
1, 1, 1, 2, 2, 1, 3, 4, 3, 1, 6, 8, 6, 4, 1, 9, 14, 15, 8, 5, 1, 16, 28, 24, 24, 10, 6, 1, 26, 44, 57, 36, 35, 12, 7, 1, 44, 86, 84, 96, 50, 48, 14, 8, 1, 73, 130, 192, 136, 145, 66, 63, 16, 9, 1, 116, 250, 270, 356, 200, 204, 84, 80, 18, 10, 1, 191, 364, 567, 476, 590, 276, 273 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

The diagonal bisections of this triangle T forms the diagonals of T^2 and T*U, where U = SHIFT_UP(T) indicates that U results from shifting each column of T up 1 row, dropping the main diagonal of all 1's.

LINKS

Table of n, a(n) for n=0..72.

FORMULA

T(2n-k,k) = Sum_{j=k..n} T(n,j)*T(j,k) = [T^2](n,k) for n>=k; odd-indexed diagonals: T(2n+1-k,k) = Sum_{j=k..n} T(n,j)*T(j+1,k) = [T*U](n,k) for n>=k; with T(n+1,n)=n+1, T(n,n)=1.

EXAMPLE

Triangle T begins:

1;

1, 1;

2, 2, 1;

3, 4, 3, 1;

6, 8, 6, 4, 1;

9, 14, 15, 8, 5, 1;

16, 28, 24, 24, 10, 6, 1;

26, 44, 57, 36, 35, 12, 7, 1;

44, 86, 84, 96, 50, 48, 14, 8, 1;

73, 130, 192, 136, 145, 66, 63, 16, 9, 1;

116, 250, 270, 356, 200, 204, 84, 80, 18, 10, 1;

191, 364, 567, 476, 590, 276, 273, 104, 99, 20, 11, 1;

294, 696, 780, 1060, 760, 906, 364, 352, 126, 120, 22, 12, 1; ...

The matrix square of T, T^2, equals the even-indexed

diagonal bisection of T, or T^2 = A118040 =

1;

2, 1;

6, 4, 1;

16, 14, 6, 1;

44, 44, 24, 8, 1;

116, 130, 84, 36, 10, 1;

294, 364, 270, 136, 50, 12, 1;

748, 990, 780, 476, 200, 66, 14, 1; ...

Let U = SHIFT_UP(T), which shifts each column of T up 1 row

and drops the main diagonal, so that U =

1;

2, 2;

3, 4, 3;

6, 8, 6, 4;

9, 14, 15, 8, 5;

16, 28, 24, 24, 10, 6; ...

Then the matrix product T*U equals the odd-indexed

diagonal bisection of T, or T*U = A118045 =

1;

3, 2;

9, 8, 3;

26, 28, 15, 4;

73, 86, 57, 24, 5;

191, 250, 192, 96, 35, 6;

500, 696, 567, 356, 145, 48, 7;

1234, 1824, 1683, 1060, 590, 204, 63, 8; ...

Thus interleaving diagonals of T^2 and T*U forms T.

MAPLE

{T(n, k)=if(n<k|k<0, 0, if(n==k, 1, if(n==k+1, n, sum(i=k, (n+k)\2, T((n+k)\2, i)*T(i+(n+k)%2, k) ))))}

CROSSREFS

Columns: A118033, A118034, A118035; A118036 (row sums), A118037 (antidiagonal sums), A118038 (central terms), A118039; diagonal bisections: A118040 (T^2), A118045 (T*U).

Sequence in context: A210789 A105809 A091594 * A089692 A066201 A193820

Adjacent sequences:  A118029 A118030 A118031 * A118033 A118034 A118035

KEYWORD

nonn,tabl

AUTHOR

Paul D. Hanna, Apr 10 2006

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified August 2 04:08 EDT 2014. Contains 245138 sequences.