cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A188106 Triangle T(n,k) with the coefficient [x^k] of 1/(1-2*x-x^2+x^3)^(n-k+1) in row n, column k.

Original entry on oeis.org

1, 1, 2, 1, 4, 5, 1, 6, 14, 11, 1, 8, 27, 42, 25, 1, 10, 44, 101, 119, 56, 1, 12, 65, 196, 342, 322, 126, 1, 14, 90, 335, 770, 1080, 847, 283, 1, 16, 119, 526, 1495, 2772, 3248, 2180, 636, 1, 18, 152, 777, 2625, 6032, 9366, 9414, 5521, 1429, 1, 20, 189, 1096, 4284, 11718, 22590, 30148, 26517, 13804, 3211
Offset: 0

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Author

L. Edson Jeffery, Mar 20 2011

Keywords

Comments

Modified versions of the generating function for D(0)={1,2,5,11,...}=A006054(m+2), m=0,1,2,..., are related to rhombus substitution tilings (see A187068, A187069 and A187070). The columns of the triangle have generating functions 1/(1-x), 2*x/(1-x)^2, x^2*(5-x)/(1-x)^3, x^3*(11-2*x-x^2)/(1-x)^4, x^4*(25-6*x-3*x^2)/(1-x)^5, ..., for which the sum of the signed coefficients in the n-th numerator equals 2^n. The diagonals {1,2,5,...}, {1,4,14,...}, ..., are generated by successive series expansion of F(n+1,x), n=0,1,..., where F(n,x)=1/(1-2*x-x^2+x^3)^n. For example, the second diagonal is {T{1,0},T{2,1},...}={1,4,14,...}=A189426, for which successive partial sums give A189427 (excluding the zero terms). Moreover, the diagonals correspond to successive convolutions of A006054 (= the first diagonal) with itself.

Examples

			1;
1, 2;
1, 4, 5;
1, 6, 14, 11;
1, 8, 27, 42, 25;
1, 10, 44, 101, 119, 56;
1, 12, 65, 196, 342, 322, 126;
1, 14, 90, 335, 770, 1080, 847, 283;
1, 16, 119, 526, 1495 ...
		

Crossrefs

Programs

  • Maple
    A188106 := proc(n,k) 1/(1-2*x-x^2+x^3)^(n-k+1) ; coeftayl(%,x=0,k) ; end proc:
    seq(seq(A188106(n,k),k=0..n),n=0..10) ; # R. J. Mathar, Mar 22 2011

Formula

Sum_{k=0..n} T(n,k) = A033505(n).
T(n,0) = 1.
T(n,2) = A014106(n-1).
T(n,3) = (n-2)*(4*n^2+2*n-9)/3.
T(n,4) = (n-2)*(n-3)*(2*n+7)*(2*n-3)/6.

Extensions

a(43) and following corrected by Georg Fischer, Oct 14 2023

A189427 Expansion of (x^2)/((1-x)*(1-2*x-x^2+x^3)^2).

Original entry on oeis.org

0, 0, 1, 5, 19, 61, 180, 502, 1349, 3529, 9050, 22854, 57014, 140832, 345036, 839530, 2030757, 4887423, 11710757, 27951471, 66486128, 157661282, 372840407, 879510801, 2070045268, 4862121660, 11398688956, 26676792832, 62333380456, 145434747140
Offset: 0

Views

Author

L. Edson Jeffery, Apr 22 2011

Keywords

Comments

Second of a series of sequences of partial sums of (nonzero) diagonals of triangle A188106 whose diagonals correspond to successive convolutions of A006054 with itself, where the first such sequence of partial sums is given by A077850. For n=1,2,..., this series of sequences is generated by successive series expansion of 1/((1-x)*(1-2*x-x^2+x^3)^n), for which A077850 corresponds to n=1 and A189427 corresponds to n=2.
a(n)=Sum_{k=0..n} A189426(k), where A189426={0,0,1,4,14,42,119,322,...} is the convolution of A006054={0,0,1,2,5,11,25,56,126,...} with itself. Also, a(n+2)=Sum_{k=0..n} A188106{n+k+1,k}, n=0,1,2,....

Crossrefs

Programs

Formula

G.f.: (x^2)/((1-x)*(1-2*x-x^2+x^3)^2).
a(n)=5*a(n-1)-6*a(n-2)-4*a(n-3)+9*a(n-4)-a(n-5)-3*a(n-6)+a(n-7), n>=7, a{m}={0,0,1,5,19,61,180}, m=0..6.
Showing 1-2 of 2 results.