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A046527
A triangle related to A000108 (Catalan) and A000302 (powers of 4).
3
1, 1, 1, 2, 5, 1, 5, 22, 9, 1, 14, 93, 58, 13, 1, 42, 386, 325, 110, 17, 1, 132, 1586, 1686, 765, 178, 21, 1, 429, 6476, 8330, 4746, 1477, 262, 25, 1, 1430, 26333, 39796, 27314, 10654, 2525, 362, 29, 1, 4862, 106762, 185517, 149052, 69930, 20754, 3973, 478, 33, 1
OFFSET
0,4
FORMULA
T(n, k) = binomial(n, k-1)*( 4^(n-k+1) - binomial(2*n, n)/binomial(2*(k-1), k-1) )/2, for n >= k >= 0, with T(n, 0) = A000108(n).
G.f. for column k: c(x)*(x/(1-4*x))^m, where c(x) = g.f. for Catalan numbers (A000108).
EXAMPLE
Triangle begins as:
1;
1, 1;
2, 5, 1;
5, 22, 9, 1;
14, 93, 58, 13, 1;
42, 386, 325, 110, 17, 1;
132, 1586, 1686, 765, 178, 21, 1;
429, 6476, 8330, 4746, 1477, 262, 25, 1;
1430, 26333, 39796, 27314, 10654, 2525, 362, 29, 1;
4862, 106762, 185517, 149052, 69930, 20754, 3973, 478, 33, 1;
MATHEMATICA
T[n_, k_]:= If[k==0, CatalanNumber[n], (1/2)*Binomial[n, k-1]*(4^(n-k+ 1) -Binomial[2*n, n]/Binomial[2*(k-1), k-1])];
Table[T[n, k], {n, 0, 12}, {k, 0, n}]//Flatten (* G. C. Greubel, Jul 28 2024 *)
PROG
(Magma)
A046527:= func< n, k | k eq 0 select Catalan(n) else (1/2)*Binomial(n, k-1)*(4^(n-k+1) - Binomial(2*n, n)/(k*Catalan(k-1))) >;
[A046527(n, k): k in [0..n], n in [0..12]]; // G. C. Greubel, Jul 28 2024
(SageMath)
def A046527(n, k):
if k==0: return catalan_number(n)
else: return (1/2)*binomial(n, k-1)*(4^(n-k+1) - binomial(2*n, n)/binomial(2*(k-1), k-1))
flatten([[A046527(n, k) for k in range(n+1)] for n in range(13)]) # G. C. Greubel, Jul 28 2024
CROSSREFS
Column sequences are: A000108 (k=0), A000346 (k=1), A018218 (k=2), A042941 (k=3), A042985 (k=4), A045505 (k=5), A045622 (k=6).
Row sums: A046814.
Sequence in context: A021803 A356273 A077382 * A378764 A008343 A257264
KEYWORD
easy,nonn,tabl
STATUS
approved

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