A140071 Triangle read by rows: iterates of X * [1,0,0,0,...]; where X = an infinite lower bidiagonal matrix with [3,1,3,1,3,1...] in the main diagonal and [1,1,1,...] in the subdiagonal.

1, 3, 1, 9, 4, 1, 27, 13, 7, 1, 81, 40, 34, 8, 1, 243, 121, 142, 42, 11, 1, 729, 364, 547, 184, 75, 12, 1, 2187, 1093, 2005, 731, 409, 87, 15, 1, 6561, 3280, 7108, 2736, 1958, 496, 132, 16, 1, 19683, 9841, 24604, 9844, 8610, 2454, 892, 148, 19, 1

Offset

1,2

Comments

Companion triangle A140070 uses an analogous operation with the main diagonal [1,3,1,3,1,3,...].

Links

Table of n, a(n) for n=1..55.

Formula

From Peter Bala, Jan 17 2014: (Start)

O.g.f. (1 + (x - 1)*z)/(1 - 4*z - (x^2 - 3)*z^2) = 1 + (x + 3)*z + (x^2 + 4*x + 9)*z^2 + ....

Recurrence equation: T(n,k) = 4*T(n-1,k) - 3*T(n-2,k) + T(n-2,k-2).

Recurrence equation for row polynomials: R(n,x) = 4*R(n-1,x) + (x^2 - 3)*R(n-2,x) with R(0,x) = 1 and R(1,x) = 3 + x.

Another recurrence equation: R(n,x) = (x + 2)*R(n-1,x) + R(n-1,-x) with R(0,x) = 1. Cf. A157751. (End)

Example

First few rows of the triangle are:
1;
3, 1;
9, 4, 1;
27, 13, 7, 1;
81, 40, 34, 8, 1;
243, 121, 142, 42, 11, 1;
729, 364, 547, 184, 75, 12, 1;
2187, 1093, 2005, 731, 409, 87, 15, 1;
6561, 3280, 7108, 2736, 1958, 496, 132, 16, 1;
...

Crossrefs

Cf. A140070, A007070 (row sums), A157751.

Sequence in context: A162852 A054448 A106516 * A285280 A285266 A067417

Adjacent sequences: A140068 A140069 A140070 * A140072 A140073 A140074

Keyword

nonn,tabl

Author

Gary W. Adamson and Roger L. Bagula, May 04 2008

Status

approved