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 1-9 of 9 results.

A212363 Number A(n,k) of Dyck n-paths all of whose ascents and descents have lengths equal to 1+k*m (m>=0); square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 5, 1, 1, 1, 1, 2, 14, 1, 1, 1, 1, 1, 4, 42, 1, 1, 1, 1, 1, 2, 8, 132, 1, 1, 1, 1, 1, 1, 4, 17, 429, 1, 1, 1, 1, 1, 1, 2, 7, 37, 1430, 1, 1, 1, 1, 1, 1, 1, 4, 12, 82, 4862, 1, 1, 1, 1, 1, 1, 1, 2, 7, 22, 185, 16796, 1
Offset: 0

Views

Author

Alois P. Heinz, May 10 2012

Keywords

Examples

			A(3,0) = 1: UDUDUD.
A(3,1) = 5: UDUDUD, UDUUDD, UUDDUD, UUDUDD, UUUDDD.
A(4,2) = 4: UDUDUDUD, UDUUUDDD, UUUDDDUD, UUUDUDDD.
A(5,2) = 8: UDUDUDUDUD, UDUDUUUDDD, UDUUUDDDUD, UDUUUDUDDD, UUUDDDUDUD, UUUDUDDDUD, UUUDUDUDDD, UUUUUDDDDD.
A(5,3) = 4: UDUDUDUDUD, UDUUUUDDDD, UUUUDDDDUD, UUUUDUDDDD.
Square array A(n,k) begins:
  1,   1,  1,  1,  1,  1,  1,  1, ...
  1,   1,  1,  1,  1,  1,  1,  1, ...
  1,   2,  1,  1,  1,  1,  1,  1, ...
  1,   5,  2,  1,  1,  1,  1,  1, ...
  1,  14,  4,  2,  1,  1,  1,  1, ...
  1,  42,  8,  4,  2,  1,  1,  1, ...
  1, 132, 17,  7,  4,  2,  1,  1, ...
  1, 429, 37, 12,  7,  4,  2,  1, ...
		

Crossrefs

Programs

  • Maple
    A:= proc(n, k) option remember;
          `if`(k=0, 1, `if`(n=0, 1, A(n-1, k)
                       +add(A(j, k)*A(n-k-j, k), j=1..n-k)))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..15);
    # second Maple program:
    A:= (n, k)-> `if`(k=0, 1, coeff(series(RootOf(
                  A||k=1+A||k*(x-x^k*(1-A||k)), A||k), x, n+1), x, n)):
    seq(seq(A(n, d-n), n=0..d), d=0..15);
  • Mathematica
    A[n_, k_] := A[n, k] = If[k == 0, 1, If[n == 0, 1, A[n-1, k] + Sum[A[j, k]*A[n-k-j, k], {j, 1, n-k}]]]; Table[Table[A[n, d-n], {n, 0, d}], {d, 0, 15}] // Flatten (* Jean-François Alcover, Jan 15 2014, translated from first Maple program *)

Formula

G.f. of column k>0 satisfies: A_k(x) = 1+A_k(x)*(x-x^k*(1-A_k(x))), g.f. of column k=0: A_0(x) = 1/(1-x).
A(n,k) = A(n-1,k) + Sum_{j=1..n-k} A(j,k)*A(n-k-j,k) for n,k>0; A(n,0) = A(0,k) = 1.
G.f. of column k > 0: (1 - x + x^k - sqrt((1 - x + x^k)^2 - 4*x^k)) / (2*x^k). - Vaclav Kotesovec, Sep 02 2014

A365699 G.f. satisfies A(x) = 1 + x^5*A(x)^2 / (1 - x*A(x)).

Original entry on oeis.org

1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 3, 6, 10, 15, 21, 33, 57, 101, 175, 291, 477, 791, 1341, 2310, 3986, 6839, 11681, 19966, 34300, 59245, 102647, 177963, 308483, 534973, 929147, 1616981, 2818967, 4920299, 8594665, 15023561, 26283971, 46030771, 80695333, 141593087
Offset: 0

Views

Author

Seiichi Manyama, Sep 16 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, n-5*k)*binomial(n-3*k+1, k)/(n-3*k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,n-5*k) * binomial(n-3*k+1,k) / (n-3*k+1).

A365700 G.f. satisfies A(x) = 1 + x^5*A(x)^3 / (1 - x*A(x)).

Original entry on oeis.org

1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 4, 8, 13, 19, 26, 46, 88, 163, 284, 466, 781, 1369, 2468, 4449, 7856, 13724, 24084, 42788, 76759, 137785, 246418, 439757, 786132, 1411148, 2541368, 4581906, 8259500, 14889781, 26871106, 48573823, 87934175, 159333544, 288857216
Offset: 0

Views

Author

Seiichi Manyama, Sep 16 2023

Keywords

Crossrefs

Programs

  • Mathematica
    terms = 43; A[] = 0; Do[A[x] = 1 + x^5*A[x]^3 / (1 - x*A[x])+ O[x]^terms // Normal, terms]; CoefficientList[A[x], x] (* Stefano Spezia, May 29 2025 *)
  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, n-5*k)*binomial(n-2*k+1, k)/(n-2*k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,n-5*k) * binomial(n-2*k+1,k) / (n-2*k+1).
a(n) ~ s*sqrt((1 - r*s)*(5 - 4*r*s)/(Pi*(3 - r*s*(3 - r*s)))) / (2*n^(3/2)*r^n), where r = 0.53247307479161512230023149440436598140650951738583 and s = 1.2504652351088857309836364363044636883260447207988... are roots of the system of equations r^5*s^3 = (s-1)*(1 - r*s), (s-1)*(3 - 2*r*s) = s*(1 - r*s). - Vaclav Kotesovec, May 29 2025

A365701 G.f. satisfies A(x) = 1 + x^5*A(x)^4 / (1 - x*A(x)).

Original entry on oeis.org

1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 5, 10, 16, 23, 31, 62, 128, 243, 423, 686, 1192, 2223, 4223, 7843, 13991, 24856, 45108, 83673, 156223, 288535, 527971, 966803, 1784663, 3319988, 6183424, 11483613, 21284475, 39499855, 73558147, 137347615, 256616567, 479231240
Offset: 0

Views

Author

Seiichi Manyama, Sep 16 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, n-5*k)*binomial(n-k+1, k)/(n-k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,n-5*k) * binomial(n-k+1,k) / (n-k+1).

A365702 G.f. satisfies A(x) = 1 + x^5*A(x)^5 / (1 - x*A(x)).

Original entry on oeis.org

1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 6, 12, 19, 27, 36, 81, 177, 341, 592, 951, 1726, 3417, 6766, 12812, 22951, 41531, 78222, 151291, 291957, 550015, 1024683, 1924543, 3671017, 7063893, 13532120, 25730347, 48840523, 93154161, 178806493, 343926597, 660308308, 1265195467
Offset: 0

Views

Author

Seiichi Manyama, Sep 16 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, n-5*k)*binomial(n+1, k))/(n+1);

Formula

a(n) = (1/(n+1)) * Sum_{k=0..floor(n/5)} binomial(n-4*k-1,n-5*k) * binomial(n+1,k).

A365698 G.f. satisfies A(x) = 1 + x^5 / (1 - x*A(x)).

Original entry on oeis.org

1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 4, 7, 11, 16, 22, 31, 47, 76, 126, 207, 331, 517, 801, 1251, 1987, 3206, 5212, 8465, 13677, 21997, 35341, 56937, 92169, 149860, 244274, 398383, 649379, 1058055, 1724575, 2814475, 4600923, 7533150, 12347908, 20252837, 33230545
Offset: 0

Views

Author

Seiichi Manyama, Sep 16 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, n-5*k)*binomial(n-5*k+1, k)/(n-5*k+1));

Formula

G.f.: A(x) = 2*(1+x^5) / (1+x+sqrt( (1+x)^2 - 4*x*(1+x^5) )).
a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,n-5*k) * binomial(n-5*k+1,k) / (n-5*k+1).

A365734 G.f. satisfies A(x) = 1 + x*A(x) / (1 - x^5*A(x)^2).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 5, 11, 21, 36, 58, 94, 163, 306, 599, 1170, 2229, 4140, 7596, 14002, 26228, 49979, 96212, 185491, 356255, 681247, 1300680, 2488500, 4782037, 9231306, 17875306, 34656389, 67194497, 130263382, 252631688, 490513867, 953923030, 1858136173, 3624102244
Offset: 0

Views

Author

Seiichi Manyama, Sep 17 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, k)*binomial(n-3*k+1, n-5*k)/(n-3*k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,k) * binomial(n-3*k+1,n-5*k) / (n-3*k+1).

A365735 G.f. satisfies A(x) = 1 + x*A(x) / (1 - x^5*A(x)^3).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 6, 16, 36, 71, 128, 223, 403, 796, 1706, 3775, 8252, 17485, 35986, 72988, 148594, 307833, 650947, 1395846, 3004732, 6443836, 13732127, 29134320, 61792707, 131525272, 281463507, 605273669, 1305373379, 2817407854, 6077804871, 13103021422
Offset: 0

Views

Author

Seiichi Manyama, Sep 17 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, k)*binomial(n-2*k+1, n-5*k)/(n-2*k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,k) * binomial(n-2*k+1,n-5*k) / (n-2*k+1).

A365736 G.f. satisfies A(x) = 1 + x*A(x) / (1 - x^5*A(x)^4).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 7, 22, 57, 127, 254, 478, 903, 1838, 4148, 10012, 24417, 58019, 132919, 295699, 649742, 1437719, 3247500, 7504925, 17607055, 41465646, 97197400, 226053017, 522505492, 1205674911, 2790322418, 6495170018, 15209566913, 35761582618
Offset: 0

Views

Author

Seiichi Manyama, Sep 17 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\5, binomial(n-4*k-1, k)*binomial(n-k+1, n-5*k)/(n-k+1));

Formula

a(n) = Sum_{k=0..floor(n/5)} binomial(n-4*k-1,k) * binomial(n-k+1,n-5*k) / (n-k+1).
Showing 1-9 of 9 results.