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 1-3 of 3 results.

A117434 Expansion of c(x*y(1+x)), c(x) the g.f. of A000108.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 0, 4, 5, 0, 0, 2, 15, 14, 0, 0, 0, 15, 56, 42, 0, 0, 0, 5, 84, 210, 132, 0, 0, 0, 0, 56, 420, 792, 429, 0, 0, 0, 0, 14, 420, 1980, 3003, 1430, 0, 0, 0, 0, 0, 210, 2640, 9009, 11440, 4862, 0, 0, 0, 0, 0, 42, 1980, 15015, 40040, 43758, 16796, 0, 0, 0, 0, 0, 0, 792, 15015, 80080, 175032, 167960, 58786
Offset: 0

Views

Author

Paul Barry, Mar 14 2006

Keywords

Examples

			Triangle begins as:
  1;
  0, 1;
  0, 1, 2;
  0, 0, 4,  5;
  0, 0, 2, 15, 14;
  0, 0, 0, 15, 56,  42;
  0, 0, 0,  5, 84, 210, 132;
  0, 0, 0,  0, 56, 420, 792, 429;
		

Crossrefs

Programs

  • Magma
    [Binomial(k, n-k)*Catalan(k): k in [0..n], n in [0..12]]; // G. C. Greubel, May 31 2021
    
  • Mathematica
    Table[CatalanNumber[k]*Binomial[k, n-k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, May 31 2021 *)
  • Sage
    flatten([[binomial(k, n-k)*catalan_number(k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, May 31 2021

Formula

T(n, k) = binomial(k, n-k)*Catalan(k).
Sum_{k=0..n} T(n, k) = A052709(n+1).
Sum_{k=0..floor(n/2)} T(n-k, k) = A115178(n) (upward diagonal sums).
T(n, k) = (-1)^(n+k)*A115179(n, k).

A328695 Rectangular array R read by descending antidiagonals: divide to each even term of the Wythoff array (A035513) by 2, and delete all others.

Original entry on oeis.org

1, 4, 2, 17, 9, 3, 72, 38, 5, 12, 305, 161, 8, 51, 6, 1292, 682, 13, 216, 10, 7, 5473, 2889, 21, 915, 16, 30, 14, 23184, 12238, 34, 3876, 26, 127, 59, 25, 98209, 51841, 55, 16419, 42, 538, 250, 106, 11, 416020, 219602, 89, 69552, 68, 2279, 1059, 449, 18, 33
Offset: 1

Views

Author

Clark Kimberling, Oct 26 2019

Keywords

Comments

Every positive integer occurs exactly once in R, and every row of R is a linear recurrence sequence. The appearance of a sequence s(r) below means that corresponding row of R is the same as s(r) except possibly for one or more initial terms of s(r).
Row 1 of R: A001076
Row 2 of R: A001077
Row 3 of R: A000045
Row 4 of R: A115179
Row 5 of R: A006355
Row 6 of R: A097924
Row 8 of R: A048875
Row 9 of R: A000032

Examples

			Row 1 of the Wythoff array is (1,2,3,5,8,13,21,34,55,89,144,...), so that row 1 of R is (1,4,17,72,...).
_______________
Northwest corner of R:
   1   4   17   72  305  1292   5473
   2   9   38  161  682  2889  12238
   3   5    8   13   21    34     55
  12  51  216  915 3876 16419  69552
   6  10   16   26   42    68    110
   7  30  127  538 2279  9654  40895
		

Crossrefs

Programs

  • Mathematica
    w[n_, k_] := Fibonacci[k + 1] Floor[n*GoldenRatio] + (n - 1) Fibonacci[k];
    Table[w[n - k + 1, k], {n, 12}, {k, n, 1, -1}] // Flatten;
    q[n_, k_] := If[Mod[w[n, k], 2] == 0, w[n, k]/2, 0];
    t[n_] := Union[Table[q[n, k], {k, 1, 50}]];
    u[n_] := If[First[t[n]] == 0, Rest[t[n]], t[n]]
    Table[u[n], {n, 1, 10}] (* A328695 array *)
    v[n_, k_] := u[n][[k]];
    Table[v[n - k + 1, k], {n, 12}, {k, n, 1, -1}] // Flatten (* A328695 sequence *)

A115399 Expansion of c(x^2-x^3), c(x) the g.f. of A000108.

Original entry on oeis.org

1, 0, -1, 1, 2, -4, -3, 15, -1, -51, 42, 154, -274, -372, 1341, 405, -5599, 2783, 20295, -27313, -61139, 160797, 124462, -767702, 94964, 3145986, -2930086, -10956466, 21290868, 29513156, -114974111, -33473459, 522016279, -279684579, -2031228003, 2867285041, 6493289367, -17791297065
Offset: 0

Views

Author

Paul Barry, Mar 14 2006

Keywords

Comments

Diagonal sums of A115179.

Crossrefs

Cf. A115178.

Formula

a(n)=sum{k=0..floor(n/2), (-1)^(n-k)*C(k)C(k,n-2k)}.
Conjecture: (n+2)*a(n) +(-n-2)*a(n-1) +4*(n-1)*a(n-2) +2*(-4*n+7)*a(n-3) +2*(2*n-5)*a(n-4)=0. - R. J. Mathar, Feb 20 2015
Showing 1-3 of 3 results.