OFFSET
4,1
COMMENTS
Interior of Pascal's triangle, stripping out the initial 1, n and final n, 1 in each row.
LINKS
Reinhard Zumkeller, Rows n = 4..120 of triangle, flattened
Hermann Stamm-Wilbrandt, Sum of Pascal's triangle reciprocals [Cached copy from the Wayback Machine]
FORMULA
T(n,k) = binomial(n, k + 2), n >= 4, 0 <= k <= n - 4.
Sum_{n >= 4, 0 <= k <= n-4} 1/T(n,k) = 3/2. - Hermann Stamm-Wilbrandt, Jul 21 2014
EXAMPLE
Triangle begins:
6;
10, 10;
15, 20, 15;
21, 35, 35, 21;
28, 56, 70, 56, 28;
36, 84, 126, 126, 84, 36;
45, 120, 210, 252, 210, 120, 45;
55, 165, 330, 462, 462, 330, 165, 55;
66, 220, 495, 792, 924, 792, 495, 220, 66;
78, 286, 715, 1287, 1716, 1716, 1287, 715, 286, 78;
91, 364, 1001, 2002, 3003, 3432, 3003, 2002, 1001, 364, 91;
105, 455, 1365, 3003, 5005, 6435, 6435, 5005, 3003, 1365, 455, 105;
...
MATHEMATICA
p[x_, n_] = ((x + 1)^n - (x^n + n*x^(n - 1) + n*x + 1))/x^2
Table[CoefficientList[p[x, n], x], {n, 4, 15}] // Flatten
PROG
(Haskell)
a144394 n k = a144394_tabl !! (n-4) !! k
a144394_row n = a144394_tabl !! (n-4)
a144394_tabl = map (drop 2 . reverse . drop 2) $ drop 4 a007318_tabl
-- Reinhard Zumkeller, Dec 24 2012
(Maxima) create_list(binomial(n, k + 2), n, 4, 20, k, 0, n - 4); /* Franck Maminirina Ramaharo, Jan 25 2019 */
CROSSREFS
KEYWORD
AUTHOR
Roger L. Bagula and Gary W. Adamson, Oct 02 2008
EXTENSIONS
Edited by Franklin T. Adams-Watters, Apr 07 2010
STATUS
approved