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 1-6 of 6 results.

A334683 Antidiagonal sums of A068914.

Original entry on oeis.org

1, 1, 2, 3, 5, 7, 12, 17, 30, 44, 79, 120, 218, 341, 625, 1001, 1848, 3016, 5603, 9283, 17342, 29085, 54606, 92513, 174456, 298111, 564333, 971563, 1845364, 3198130, 6092038, 10621153, 20282471, 35554559, 68042537, 119874494, 229840130, 406794862, 781246800, 1388643835
Offset: 0

Views

Author

Stefano Spezia, May 08 2020

Keywords

Crossrefs

Cf. A068914.

Programs

  • Mathematica
    T[n_,k_]:=Sum[(-1)^j*Binomial[n,Floor[(n+(k+2)j)/2]],{j,Floor[-n/(k+2)],Ceiling[n/(k+2)]}]; Table[Sum[T[n-k,k],{k,0,n}],{n,0,39}]
  • PARI
    T(n,k) = sum(j=floor(-n/(k+2)), ceil(n/(k+2)), (-1)^j*binomial(n,floor((n+(k+2)*j)/2))); \\ A068914
    a(n) = sum(k=0, n, T(n-k, k)); \\ Michel Marcus, May 09 2020

A216226 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=1 or if k-n>=4, T(0,0) = T(0,1) = T(0,2) = T(0,3) = 1, T(n,k) = T(n-1,k) + T(n,k-1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 0, 3, 2, 0, 0, 0, 3, 5, 0, 0, 0, 0, 0, 8, 5, 0, 0, 0, 0, 0, 8, 13, 0, 0, 0, 0, 0, 0, 0, 21, 13, 0, 0, 0, 0, 0, 0, 0, 21, 34, 0, 0, 0, 0, 0, 0, 0, 0, 0, 55, 34, 0, 0, 0, 0, 0
Offset: 0

Views

Author

Philippe Deléham, Mar 13 2013

Keywords

Examples

			Square array begins:
1, 1, 1, 1,  0,  0,  0,   0,   0, 0, ... row n=0
0, 1, 2, 3,  3,  0,  0,   0,   0, 0, ... row n=1
0, 0, 2, 5,  8,  8,  0,   0,   0, 0, ... row n=2
0, 0, 0, 5, 13, 21, 21,   0,   0, 0, ... row n=3
0, 0, 0, 0, 13, 34, 55,  55,   0, 0, ... row n=4
0, 0, 0, 0,  0, 34, 89, 144, 144, 0, ... row n=5
...
		

Crossrefs

Cf. A000045 (Fibonacci numbers), A000285, A001519, A001906, A068914

Formula

T(n,n) = A000045(2*n-1) = A001519(n).
T(n,n+1) = A000045(2*n+1) = A001519(n+1).
T(n,n+2) = T(n,n+3) = A000045(2*n+2) = A001906(n+1).
Sum_{k, 0<=k<=n} T(n-k,k) = A000045(n+1).
Sum_{k, k>=0} T(n,k) = A000285(2*n+1).
Sum_{n, n>=0} T(n,k) = A000285(2*k-2), k>=2.

A216228 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=1 or if k-n>=3, T(0,0) = T(0,1) = T(0,2) = 1, T(n,k) = T(n-1,k) + T(n,k-1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 0, 2, 0, 0, 0, 2, 2, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 4, 4, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 8, 8, 0, 0, 0, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 32
Offset: 0

Views

Author

Philippe Deléham, Mar 13 2013

Keywords

Comments

An arithmetic hexagon of E. Lucas.

Examples

			Square array begins:
1, 1, 1, 0, 0,  0,  0,  0, ... row n=0
0, 1, 2, 2, 0,  0,  0,  0, ... row n=1
0, 0, 2, 4, 4,  0,  0,  0, ... row n=2
0, 0, 0, 4, 8,  8,  0,  0, ... row n=3
0, 0, 0, 0, 8, 16, 16,  0, ... row n=4
0, 0, 0, 0, 0, 16, 32, 32, ... row n=5
...
		

References

  • E. Lucas, Théorie des nombres, Albert Blanchard, Paris 1958, Tome 1, p.89

Crossrefs

Formula

T(n,n) = A011782(n).
T(n,n+1) = T(n,n+2) = 2^n = A000079(n).
Sum_{k, 0<=k<=n} T(n-k,k) = A016116(n).
Sum_{n, n>=0} T(n,k) = A084215(k).
Sum_{k, k>=0} T(n,k) = A084215(n+1), n>=1.

A216230 Square array T, read by antidiagonals: T(n,k) = 0 if n-k>=1 or if k-n>=2, T(0,0) = T(0,1) = 1, T(n,k) = T(n-1,k) + T(n,k-1).

Original entry on oeis.org

1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 0

Views

Author

Philippe Deléham, Mar 14 2013

Keywords

Examples

			Square array begins:
1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...
0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...
0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, ...
0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, ...
0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, ...
0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, ...
0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, ...
0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, ...
...
		

Crossrefs

Formula

T(n,n) = T(n,n+1) = 1.
Sum_{k, 0<=k<=n} T(n-k, k) = 1.

A132890 Triangle read by rows: T(n,k) is the number of left factors of Dyck paths of length n that have height k (1 <= k <= n).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 4, 1, 1, 1, 7, 5, 5, 1, 1, 1, 7, 13, 6, 6, 1, 1, 1, 15, 18, 20, 7, 7, 1, 1, 1, 15, 39, 26, 27, 8, 8, 1, 1, 1, 31, 57, 73, 35, 35, 9, 9, 1, 1, 1, 31, 112, 99, 109, 44, 44, 10, 10, 1, 1, 1, 63, 169, 253, 152, 154, 54, 54, 11, 11, 1, 1
Offset: 1

Views

Author

Emeric Deutsch, Sep 08 2007

Keywords

Comments

Sum of terms in row n = binomial(n, floor(n/2)) = A001405(n).
T(n,2) = A052551(n-2) (n >= 2).
T(n,3) = A005672(n) = Fibonacci(n+1) - 2^floor(n/2).
Sum_{k=1..n} k*T(n,k) = A132891(n).

Examples

			T(5,3)=4 because we have UDUUU, UUDUU, UUUDD and UUUDU, where U=(1,1) and D=(1,-1).
Triangle starts:
  1;
  1, 1;
  1, 1, 1;
  1, 3, 1, 1;
  1, 3, 4, 1; 1;
  1, 7, 5, 5, 1, 1;
		

Crossrefs

Programs

  • Maple
    v := ((1-sqrt(1-4*z^2))*1/2)/z: g := proc (k) options operator, arrow: v^k*(1+v)*(1+v^2)/((1+v^(k+1))*(1+v^(k+2))) end proc: T := proc (n, k) options operator, arrow: coeff(series(g(k), z = 0, 50), z, n) end proc: for n from 0 to 12 do seq(T(n, k), k = 1 .. n) end do; # yields sequence in triangular form
    # second Maple program:
    b:= proc(x, y, k) option remember; `if`(x=0, z^k, `if`(y>0,
          b(x-2, y-1, k), 0)+ b(x-2, y+1, max(y+1, k)))
        end:
    T:= n-> (p-> seq(coeff(p, z, i), i=1..n))(b(2*n, 0$2)):
    seq(T(n), n=1..16);  # Alois P. Heinz, Sep 05 2017
  • Mathematica
    b[x_, y_, k_] := b[x, y, k] = If[x == 0, z^k, If[y > 0, b[x - 2, y - 1, k], 0] + b[x - 2, y + 1, Max[y + 1, k]]];
    T[n_] := Function[p, Table[Coefficient[p, z, i], {i, 1, n}]][b[2n, 0, 0]];
    Table[T[n], {n, 1, 16}] // Flatten (* Jean-François Alcover, Apr 01 2018, after Alois P. Heinz *)

Formula

The g.f. of column k is g(k, z) = v^k*(1+v)*(1+v^2)*/((1+v^(k+1))*(1+v^(k+2))), where v = (1-sqrt(1-4*z^2))/(2*z). (Obtained as the difference G(k,z)-G(k-1,z), where G(k,z) is given in the R. Kemp reference (p. 159).)

Extensions

Keyword tabl added by Michel Marcus, Apr 09 2013

A069713 As a square array T(n,k) by antidiagonals, number of ways of partitioning k into up to n parts each no more than 5, or into up to 5 parts each no more than n; as a triangle t(n,k), number of ways of partitioning n into exactly k parts each no more than 6 (i.e., of arranging k indistinguishable standard dice to produce a total of n).

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 2, 1, 1, 0, 1, 2, 2, 1, 1, 0, 1, 3, 3, 2, 1, 1, 0, 0, 3, 4, 3, 2, 1, 1, 0, 0, 3, 5, 5, 3, 2, 1, 1, 0, 0, 2, 6, 6, 5, 3, 2, 1, 1, 0, 0, 2, 6, 8, 7, 5, 3, 2, 1, 1, 0, 0, 1, 6, 9, 9, 7, 5, 3, 2, 1, 1, 0, 0, 1, 6, 11, 11, 10, 7, 5, 3, 2, 1, 1, 0, 0, 0, 5, 11, 14, 12, 10, 7, 5
Offset: 0

Views

Author

Henry Bottomley, Apr 01 2002

Keywords

Examples

			As square array, rows start: 1,0,0,0,0,0,...; 1,1,1,1,1,1,...; 1,1,2,2,3,3,...; 1,1,2,3,4,5,...; 1,1,2,3,5,6,...; 1,1,2,3,5,7,...; etc. As triangle, rows start: 1; 0,1; 0,1,1; 0,1,1,1; 0,1,2,1,1; 0,1,2,2,1,1; 0,1,3,3,2,1,1; etc. T(3,7)=6 since 7 can be written as 5+2, 5+1+1, 4+3, 4+2+1, 3+3+1, 3+2+2; or alternatively as 2+2+1+1+1, 3+1+1+1, 2+2+2+1, 3+2+1+1, 3+2+2, 3+3+1. t(10,3)=6 since 10 can be written as 6+3+1, 6+2+2, 5+4+1, 5+3+2, 4+4+2, 4+3+3.
		

Crossrefs

Cf. A061676 for a similar triangle, though with distinguishable dice (and a different offset). Antidiagonal sums of T(n, k), i.e., row sums (over k) of t(n, k), are A001402. First 22 terms are same as A068914 (see formula).

Formula

If k<6 T(n,k) = A068914(n,k). T(n,k) = T(n,5n-k); t(n,k) = t(7n-k,k). T(floor(5n/2),n) = t(n,floor(7n/2)) = A001975(n).
Showing 1-6 of 6 results.