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A092565 Triangle of coefficients T(n,k) (n>=0, 0<=k<=2n), read by rows, where the n-th row polynomial equals the numerator of the n-th convergent of the continued fraction [1+x+x^2;1+x+x^2,1+x+x^2,...] for n>0, with the zeroth row defined as T(0,0)=1. 2
1, 1, 1, 1, 2, 2, 3, 2, 1, 3, 5, 8, 7, 6, 3, 1, 5, 10, 19, 22, 22, 16, 10, 4, 1, 8, 20, 42, 58, 69, 63, 49, 30, 15, 5, 1, 13, 38, 89, 142, 191, 206, 191, 146, 95, 50, 21, 6, 1, 21, 71, 182, 327, 491, 602, 637, 573, 447, 296, 167, 77, 28, 7, 1, 34, 130, 363, 722, 1191, 1626 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

T(n,k) is the number of lattice paths from (0,0) to (n,k) using steps (1,0),(2,0),(1,1),(1,2). [Joerg Arndt, Jul 01 2011]

Diagonal forms A092566, row sums form A006190. Column T(n,0) forms Fibonacci numbers A000045, T(n,1) forms A001629.

LINKS

Alois P. Heinz, Rows n = 0..100, flattened

FORMULA

n-th row polynomial R(n) = sum_{k=0..n} A037027(n, k)*x^k*(1+x)^k; R(n+1)/R(n) = [1+x+x^2;1+x+x^2, ...(n+1)times..., 1+x+x^2] for n>=0; R(0)=1.

EXAMPLE

Ratio of row polynomials R(3)/R(2) = (3+5*x+8*x^2+7*x^3+6*x^4+3*x^5+x^6)/(2+2*x+3*x^2+2*x^3+x^4) = [1+x+x^2;1+x+x^2,1+x+x^2].

Rows begin:

1;

1, 1, 1;

2, 2, 3, 2, 1;

3, 5, 8, 7, 6, 3, 1;

5, 10, 19, 22, 22, 16, 10, 4, 1;

8, 20, 42, 58, 69, 63, 49, 30, 15, 5, 1;

13, 38, 89, 142, 191, 206, 191, 146, 95, 50, 21, 6, 1;

21, 71, 182, 327, 491, 602, 637, 573, 447, 296, 167, 77, 28, 7, 1;

34, 130, 363, 722, 1191, 1626, 1921, 1958, 1752, 1366, 931, 546, 273, 112, 36, 8, 1;

...

MAPLE

T:= proc(x, y) option remember; `if`(y<0 or y>2*x, 0, `if`(x=0, 1,

      add(T(x-l[1], y-l[2]), l=[[1, 0], [2, 0], [1, 1], [1, 2]])))

    end:

seq(seq(T(n, k), k=0..2*n), n=0..10); # Alois P. Heinz, Apr 16 2013

MATHEMATICA

A037027[n_, k_] := Sum[Binomial[k+j, k]*Binomial[j, n-j-k], {j, 0, n-k}]; A037027[n_, 0] = Fibonacci[n + 1]; row[n_] := CoefficientList[ Sum[A037027[n, k] x^k (1+x)^k, {k, 0, n}], x]; Flatten[Table[row[n], {n, 0, 8}]][[1 ;; 70]] (* Jean-Fran├žois Alcover, Jul 18 2011 *)

PROG

(PARI) T(n, k)=if(2*n<k || k<0, 0, polcoeff(contfracpnqn(vector(n, i, 1+x+x^2))[1, 1], k, x))

(PARI) /* same as in A092566, but last line (output) replaced by the following */

/* show as triangle (0<=k<=2*n): */

{for (n=1, N, for (k=1, 2*n-1, print1(M[n, k], ", "); ); print(); ); }

/* Joerg Arndt, Jul 01 2011 */

CROSSREFS

Cf. A092566, A037027.

Sequence in context: A242266 A239617 A304737 * A021452 A093420 A104897

Adjacent sequences:  A092562 A092563 A092564 * A092566 A092567 A092568

KEYWORD

nonn,tabf

AUTHOR

Paul D. Hanna, Feb 28 2004

STATUS

approved

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Last modified September 30 18:12 EDT 2020. Contains 337440 sequences. (Running on oeis4.)