

A131338


Triangle, read by rows of n*(n+1)/2 + 1 terms, that starts with a '1' in row 0 with row n consisting of n '1's followed by the partial sums of the prior row.


8



1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 3, 5, 1, 1, 1, 1, 1, 2, 3, 4, 6, 9, 14, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 7, 10, 14, 20, 29, 43, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 8, 11, 15, 20, 27, 37, 51, 71, 100, 143, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 9, 12, 16, 21, 27, 35, 46, 61, 81, 108, 145, 196
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OFFSET

0,7


LINKS

Paul D. Hanna, Rows n = 0..16, flattened.


FORMULA

T(n,k) = Sum_{i=0..kn} T(n1,i) for k>n, else T(n,k)=1 for n>=k>=0.
Right border: T(n+1, (n+1)*(n+2)/2) = A098569(n) = Sum_{k=0..n} C( (k+1)*(k+2)/2 + nk1, nk).
T(n, n*(n1)/2 + 1) = Sum_{k=0..n1} C(k*(k+1)/2, nk) = A121690(n1) for n>=1.  Paul D. Hanna, Aug 30 2007


EXAMPLE

Triangle begins:
1;
1, 1;
1,1, 1,2;
1,1,1, 1,2,3,5;
1,1,1,1, 1,2,3,4,6,9,14;
1,1,1,1,1, 1,2,3,4,5,7,10,14,20,29,43;
1,1,1,1,1,1, 1,2,3,4,5,6,8,11,15,20,27,37,51,71,100,143;
1,1,1,1,1,1,1, 1,2,3,4,5,6,7,9,12,16,21,27,35,46,61,81,108,145,196,267,367,510; ...
Row sums equal the row sums (A098569) of triangle A098568,
where A098568(n, k) = binomial( (k+1)*(k+2)/2 + nk1, nk):
1;
1, 1;
1, 3, 1;
1, 6, 6, 1;
1, 10, 21, 10, 1;
1, 15, 56, 55, 15, 1;
1, 21, 126, 220, 120, 21, 1; ...


PROG

(PARI) {T(n, k)=if(k>n*(n+1)/2k<0, 0, if(k<=n, 1, sum(i=0, kn, T(n1, i))))}
for(n=0, 10, for(k=0, n*(n+1)/2, print1(T(n, k), ", ")); print(""))


CROSSREFS

Cf. A098568, A098569 (row sums), A121690, A183202.
Cf. A214403 (variant).
Sequence in context: A220091 A063746 A201075 * A242784 A106498 A093466
Adjacent sequences: A131335 A131336 A131337 * A131339 A131340 A131341


KEYWORD

nonn,tabl


AUTHOR

Paul D. Hanna, Jun 29 2007


STATUS

approved



