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.

Showing 1-4 of 4 results.

A124747 Inverse of number triangle A124744.

Original entry on oeis.org

1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 2, 2, 2, 1, 0, 0, 3, 3, 3, 2, 1, 0, 0, 7, 7, 7, 5, 3, 1, 0, 0, 12, 12, 12, 9, 6, 3, 1, 0, 0, 30, 30, 30, 23, 16, 9, 4, 1, 0, 0, 55, 55, 55, 43, 31, 19, 10, 4, 1
Offset: 0

Views

Author

Paul Barry, Nov 06 2006

Keywords

Comments

Third column and row sums give A047749.

Examples

			Triangle begins
1,
0, 1,
0, 0, 1,
0, 0, 1, 1,
0, 0, 1, 1, 1,
0, 0, 2, 2, 2, 1,
0, 0, 3, 3, 3, 2, 1,
0, 0, 7, 7, 7, 5, 3, 1,
0, 0, 12, 12, 12, 9, 6, 3, 1
		

A124745 Expansion of (1+x)/(1-x^2+x^3).

Original entry on oeis.org

1, 1, 1, 0, 0, -1, 0, -1, 1, -1, 2, -2, 3, -4, 5, -7, 9, -12, 16, -21, 28, -37, 49, -65, 86, -114, 151, -200, 265, -351, 465, -616, 816, -1081, 1432, -1897, 2513, -3329, 4410, -5842, 7739, -10252, 13581, -17991, 23833, -31572, 41824, -55405, 73396, -97229, 128801
Offset: 0

Views

Author

Paul Barry, Nov 06 2006

Keywords

Crossrefs

Row sums of A124744.
The following are basically all variants of the same sequence: A000931, A078027, A096231, A124745, A133034, A134816, A164001, A182097, A228361 and probably A020720. However, each one has its own special features and deserves its own entry.

Programs

  • Mathematica
    LinearRecurrence[{0, 1, -1}, {1, 1, 1}, 100] (* Paolo Xausa, Aug 27 2024 *)

Formula

a(n) = Sum_{k=0..n} C(floor(k/2),n-k)*(-1)^(n-k) = (-1)^n*A078027(n).
a(n) = a(n-2) - a(n-3) with a(0) = a(1) = a(2) = 1. - Taras Goy, Mar 24 2019

A124746 Expansion of (1+x^2)/(1-x^4+x^5).

Original entry on oeis.org

1, 0, 1, 0, 1, -1, 1, -1, 1, -2, 2, -2, 2, -3, 4, -4, 4, -5, 7, -8, 8, -9, 12, -15, 16, -17, 21, -27, 31, -33, 38, -48, 58, -64, 71, -86, 106, -122, 135, -157, 192, -228, 257, -292, 349, -420, 485, -549, 641, -769, 905, -1034, 1190, -1410, 1674, -1939, 2224, -2600
Offset: 0

Views

Author

Paul Barry, Nov 06 2006

Keywords

Crossrefs

Diagonal sums of A124744.
Cf. A124789.

Programs

  • Mathematica
    LinearRecurrence[{0, 0, 0, 1, -1}, {1, 0, 1, 0, 1}, 100] (* Paolo Xausa, Aug 27 2024 *)

Formula

a(n) = Sum_{k=0..floor(n/2)} C(floor(k/2),n-2k)*(-1)^n.
a(n) = (-1)^n*A124789(n). - R. J. Mathar, Jun 30 2020

A124749 Expansion of (1+x*y+x^2*y^2)/(1-x^3*y^3+x^4*y^3).

Original entry on oeis.org

1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, -1, 1, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, 0, 0, -2, 1, 0, 0, 0, 0, 0, 0, 1, -2, 1, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, -3, 1
Offset: 0

Views

Author

Paul Barry, Nov 06 2006

Keywords

Comments

Row sums are A124750. Diagonal sums are A124751. Inverse is A124752.

Examples

			Triangle begins
1,
0, 1,
0, 0, 1,
0, 0, 0, 1,
0, 0, 0, -1, 1,
0, 0, 0, 0, -1, 1,
0, 0, 0, 0, 0, -1, 1,
0, 0, 0, 0, 0, 0, -2, 1,
0, 0, 0, 0, 0, 0, 1, -2, 1,
0, 0, 0, 0, 0, 0, 0, 1, -2, 1,
0, 0, 0, 0, 0, 0, 0, 0, 1, -3, 1
		

Crossrefs

Cf. A124744.

Formula

Number triangle T(n,k)=C(floor(k/3),n-k)*(-1)^(n-k)
G.f. of column k is x^k*(1-x)^floor(k/3); - Paul Barry, Dec 14 2006
Showing 1-4 of 4 results.