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A052509 Knights-move Pascal triangle: T(n,k), n >= 0, 0 <= k <= n; T(n,0) = T(n,n) = 1, T(n,k) = T(n-1,k) + T(n-2,k-1) for k = 1,2,...,n-1, n >= 2. 17
1, 1, 1, 1, 2, 1, 1, 3, 2, 1, 1, 4, 4, 2, 1, 1, 5, 7, 4, 2, 1, 1, 6, 11, 8, 4, 2, 1, 1, 7, 16, 15, 8, 4, 2, 1, 1, 8, 22, 26, 16, 8, 4, 2, 1, 1, 9, 29, 42, 31, 16, 8, 4, 2, 1, 1, 10, 37, 64, 57, 32, 16, 8, 4, 2, 1, 1, 11, 46, 93, 99, 63, 32, 16, 8, 4, 2, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Also square array T(n,k) (n >= 0, k >= 0) read by antidiagonals: T(n,k) = Sum_{i=0..k} C(n,i).

As a number triangle read by rows, this is T(n,k) = sum{i=n-2*k..n-k, binomial(n-k,i)}, with T(n,k) = T(n-1,k) + T(n-2,k-1). Row sums are A000071(n+2). Diagonal sums are A023435(n+1). It is the reverse of the Whitney triangle A004070. - Paul Barry, Sep 04 2005

LINKS

Reinhard Zumkeller, Rows n = 0..150 of triangle, flattened

D. J. Price, Some unusual series occurring in n-dimensional geometry, Math. Gaz., 30 (1946), 149-150.

Index entries for triangles and arrays related to Pascal's triangle

FORMULA

T(n, k) = sum(m=0..n, C(n-k, k-m) ). - Wouter Meeussen, Oct 03 2002

EXAMPLE

Triangle begins:

1

1,1

1,2,1

1,3,2,1

1,4,4,2,1

1,5,7,4,2,1

1,6,11,8,4,2,1

As a square array, this begins:

1 1 1 1 1 1 ...

1 2 2 2 2 2 ...

1 3 4 4 4 4 ...

1 4 7 8 8 8 ...

1 5 11 15 16 ...

1 6 16 26 31 32 ...

MAPLE

a := proc(n::nonnegint, k::nonnegint) option remember: if k=0 then RETURN(1) fi: if k=n then RETURN(1) fi: a(n-1, k)+a(n-2, k-1) end: for n from 0 to 11 do for k from 0 to n do printf(`%d, `, a(n, k)) od: od: # James A. Sellers, Mar 17 2000

with(combinat): for s from 0 to 11 do for n from s to 0 by -1 do if n=0 or s-n=0 then printf(`%d, `, 1) else printf(`%d, `, sum(binomial(n, i), i=0..s-n)) fi; od: od: # James A. Sellers, Mar 17 2000

MATHEMATICA

Table[Sum[Binomial[n-k, k-m], {m, 0, n}], {n, 0, 10}, {k, 0, n}]

PROG

(PARI) T(n, k)=sum(m=0, n, binomial(n-k, k-m));

for(n=0, 10, for(k=0, n, print1(T(n, k), ", "); ); print(); ); /* show triangle */

(Haskell)

a052509 n k = a052509_tabl !! n !! k

a052509_row n = a052509_tabl !! n

a052509_tabl = [1] : [1, 1] : f [1] [1, 1] where

   f row' row = rs : f row rs where

     rs = zipWith (+) ([0] ++ row' ++ [1]) (row ++ [0])

-- Reinhard Zumkeller, Nov 22 2012

CROSSREFS

Cf. A054123, A054124, A007318, A008949.

Row sums A000071; Diagonal sums A023435; Mirror A004070.

Columns give A000027, A000124, A000125, A000127, A006261, ...

Cf. A052509, A054123, A054124, A007318, A008949, A052553.

Partial sums across rows of (extended) Pascal's triangle A052553.

Sequence in context: A194005 A055794 A092905 * A172119 A228125 A227588

Adjacent sequences:  A052506 A052507 A052508 * A052510 A052511 A052512

KEYWORD

nonn,tabl,easy,nice

AUTHOR

N. J. A. Sloane, Mar 17 2000

EXTENSIONS

More terms from James A. Sellers, Mar 17 2000

Entry formed by merging two earlier entries. - N. J. A. Sloane, Jun 17 2007

Edited by Johannes W. Meijer, Jul 24 2011

STATUS

approved

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Last modified August 29 03:31 EDT 2015. Contains 261184 sequences.