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 1-8 of 8 results.

A291382 p-INVERT of (1,1,0,0,0,0,...), where p(S) = 1 - 2 S - S^2.

Original entry on oeis.org

2, 7, 22, 70, 222, 705, 2238, 7105, 22556, 71608, 227332, 721705, 2291178, 7273743, 23091762, 73308814, 232731578, 738846865, 2345597854, 7446508273, 23640235416, 75050038224, 238259397096, 756395887969, 2401310279090, 7623377054503, 24201736119310
Offset: 0

Views

Author

Clark Kimberling, Sep 04 2017

Keywords

Comments

Suppose s = (c(0), c(1), c(2), ...) is a sequence and p(S) is a polynomial. Let S(x) = c(0)*x + c(1)*x^2 + c(2)*x^3 + ... and T(x) = (-p(0) + 1/p(S(x)))/x. The p-INVERT of s is the sequence t(s) of coefficients in the Maclaurin series for T(x). Taking p(S) = 1 - S gives the "INVERT" transform of s, so that p-INVERT is a generalization of the "INVERT" transform (e.g., A033453).
In the following guide to p-INVERT sequences using s = (1,1,0,0,0,...) = A019590, in some cases t(1,1,0,0,0,...) is a shifted version of the cited sequence:
p(S) t(1,1,0,0,0,...)
1 - S A000045 (Fibonacci numbers)
1 - S^2 A094686
1 - S^3 A115055
1 - S^4 A291379
1 - S^5 A281380
1 - S^6 A281381
1 - 2 S A002605
1 - 3 S A125145
(1 - S)^2 A001629
(1 - S)^3 A001628
(1 - S)^4 A001629
(1 - S)^5 A001873
(1 - S)^6 A001874
1 - S - S^2 A123392
1 - 2 S - S^2 A291382
1 - S - 2 S^2 A124861
1 - 2 S - S^2 A291383
(1 - 2 S)^2 A073388
(1 - 3 S)^2 A291387
(1 - 5 S)^2 A291389
(1 - 6 S)^2 A291391
(1 - S)(1 - 2 S) A291393
(1 - S)(1 - 3 S) A291394
(1 - 2 S)(1 - 3 S) A291395
(1 - S)(1 - 2 S) A291393
(1 - S)(1 - 2 S)(1 - 3 S) A291396
1 - S - S^3 A291397
1 - S^2 - S^3 A291398
1 - S - S^2 - S^3 A186812
1 - S - S^2 - S^3 - S^4 A291399
1 - S^2 - S^4 A291400
1 - S - S^4 A291401
1 - S^3 - S^4 A291402
1 - 2 S^2 - S^4 A291403
1 - S^2 - 2 S^4 A291404
1 - 2 S^2 - 2 S^4 A291405
1 - S^3 - S^6 A291407
(1 - S)(1 - S^2) A291408
(1 - S^2)(1 - S)^2 A291409
1 - S - S^2 - 2 S^3 A291410
1 - 2 S - S^2 + S^3 A291411
1 - S - 2 S^2 + S^3 A291412
1 - 3 S + S^2 + S^3 A291413
1 - 2 S + S^3 A291414
1 - 3 S + S^2 A291415
1 - 4 S + S^2 A291416
1 - 4 S + 2 S^2 A291417

Crossrefs

Programs

  • Mathematica
    z = 60; s = x + x^2; p = 1 - 2 s - s^2;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A019590 *)
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A291382 *)

Formula

G.f.: (-2 - 3 x - 2 x^2 - x^3)/(-1 + 2 x + 3 x^2 + 2 x^3 + x^4).
a(n) = 2*a(n-1) + 3*a(n-2) + 2*a(n-3) + a(n-4) for n >= 5.

A361568 Expansion of e.g.f. exp(x^3/6 * (1+x)^3).

Original entry on oeis.org

1, 0, 0, 1, 12, 60, 130, 420, 8400, 101080, 781200, 4435200, 37714600, 607807200, 8660652000, 94007313400, 914497584000, 11566931376000, 198256136478400, 3275456501116800, 46558791351072000, 636647461257808000, 10238792220969312000, 194852563745775936000
Offset: 0

Views

Author

Seiichi Manyama, Mar 16 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x^3/6*(1+x)^3)))
    
  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=(i-1)!/6*sum(j=3, i, j*binomial(3, j-3)*v[i-j+1]/(i-j)!)); v;

Formula

a(n) = n! * Sum_{k=0..floor(n/3)} binomial(3*k,n-3*k)/(6^k * k!).
a(0) = 1; a(n) = ((n-1)!/6) * Sum_{k=3..n} k * binomial(3,k-3) * a(n-k)/(n-k)!.
a(n) = (n-1)*(n-2)/6 * (3*a(n-3) + 12*(n-3)*a(n-4) + 15*(n-3)*(n-4)*a(n-5) + 6*(n-3)*(n-4)*(n-5)*a(n-6)). -Seiichi Manyama, Jun 16 2024

A361730 Diagonal of rational function 1/(1 - (1 + x*y*z) * (x^3 + y^3 + z^3)).

Original entry on oeis.org

1, 0, 0, 6, 18, 18, 96, 540, 1350, 3480, 16470, 61020, 175860, 627480, 2498580, 8520876, 28563570, 106917300, 393495396, 1369171188, 4914119826, 18191218716, 65741140080, 235643531508, 862450963704, 3163777886412, 11484836808588, 41875694151720
Offset: 0

Views

Author

Seiichi Manyama, Mar 22 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\3, (3*k)!/k!^3*binomial(3*k, n-3*k));

Formula

a(n) = Sum_{k=0..floor(n/3)} (3*k)!/k!^3 * binomial(3*k,n-3*k).
From Vaclav Kotesovec, Mar 22 2023: (Start)
Recurrence: (n-1)*n^2*a(n) = -(n-1)^2*n*a(n-1) + 27*(n-2)*(n-1)^2*a(n-3) + 108*(n-2)*(n^2 - 3*n + 1)*a(n-4) + 54*(3*n^3 - 18*n^2 + 28*n - 5)*a(n-5) + 108*(n^3 - 7*n^2 + 12*n - 1)*a(n-6) + 27*(n-5)*(n-3)*n*a(n-7).
a(n) ~ sqrt(3) * ((3 + sqrt(21))/2)^n / (2*Pi*n). (End)

A378151 G.f. A(x) satisfies A(x) = 1 + (x * (1+x) * A(x))^3.

Original entry on oeis.org

1, 0, 0, 1, 3, 3, 4, 18, 45, 72, 153, 450, 1066, 2172, 5142, 13381, 31752, 72333, 176475, 441909, 1065528, 2551465, 6292857, 15620439, 38229235, 93698523, 232545105, 578019090, 1430290512, 3548336724, 8851036863, 22092054588, 55093739760, 137681640450
Offset: 0

Views

Author

Seiichi Manyama, Nov 18 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\3, binomial(3*k, n-3*k)*binomial(3*k, k)/(2*k+1));

Formula

a(n) = Sum_{k=0..floor(n/3)} binomial(3*k,n-3*k) * binomial(3*k,k)/(2*k+1).

A375318 Expansion of 1/(1 - x^3*(1 + x)^4).

Original entry on oeis.org

1, 0, 0, 1, 4, 6, 5, 9, 28, 57, 82, 122, 249, 519, 913, 1485, 2632, 5053, 9369, 16375, 28662, 52226, 96182, 173220, 307653, 551927, 1002327, 1815191, 3258813, 5845015, 10539893, 19048900, 34332648, 61735922, 111129005, 200406479, 361364501, 650804074, 1171717523
Offset: 0

Views

Author

Seiichi Manyama, Aug 12 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=40, x='x+O('x^N)); Vec(1/(1-x^3*(1+x)^4))
    
  • PARI
    a(n) = sum(k=0, n\3, binomial(4*k, n-3*k));

Formula

a(n) = a(n-3) + 4*a(n-4) + 6*a(n-5) + 4*a(n-6) + a(n-7).
a(n) = Sum_{k=0..floor(n/3)} binomial(4*k,n-3*k).

A375319 Expansion of (1 + x)/(1 - x^3*(1 + x)^3).

Original entry on oeis.org

1, 1, 0, 1, 4, 6, 5, 8, 21, 36, 45, 66, 128, 224, 330, 497, 851, 1452, 2287, 3556, 5826, 9693, 15624, 24807, 40126, 65737, 106584, 171112, 276160, 448980, 728201, 1174985, 1897380, 3074733, 4982688, 8055918, 13020029, 21074012, 34125561, 55210580, 89284541
Offset: 0

Views

Author

Seiichi Manyama, Aug 12 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=50, x='x+O('x^N)); Vec((1+x)/(1-x^3*(1+x)^3))
    
  • PARI
    a(n) = sum(k=0, n\3, binomial(3*k+1, n-3*k));

Formula

a(n) = a(n-3) + 3*a(n-4) + 3*a(n-5) + a(n-6).
a(n) = Sum_{k=0..floor(n/3)} binomial(3*k+1,n-3*k).

A375321 Expansion of (1 + x)^2/(1 - x^3*(1 + x)^3).

Original entry on oeis.org

1, 2, 1, 1, 5, 10, 11, 13, 29, 57, 81, 111, 194, 352, 554, 827, 1348, 2303, 3739, 5843, 9382, 15519, 25317, 40431, 64933, 105863, 172321, 277696, 447272, 725140, 1177181, 1903186, 3072365, 4972113, 8057421, 13038606, 21075947, 34094041, 55199573, 89336141
Offset: 0

Views

Author

Seiichi Manyama, Aug 12 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=40, x='x+O('x^N)); Vec((1+x)^2/(1-x^3*(1+x)^3))
    
  • PARI
    a(n) = sum(k=0, n\3, binomial(3*k+2, n-3*k));

Formula

a(n) = a(n-3) + 3*a(n-4) + 3*a(n-5) + a(n-6).
a(n) = Sum_{k=0..floor(n/3)} binomial(3*k+2,n-3*k).
a(n) = A375319(n) + A375319(n-1).

A378153 G.f. A(x) satisfies A(x) = 1 + (x * (1+x))^3 * A(x)^2.

Original entry on oeis.org

1, 0, 0, 1, 3, 3, 3, 12, 30, 45, 75, 192, 436, 798, 1554, 3542, 7740, 15543, 32183, 70794, 153252, 321431, 684123, 1491504, 3232672, 6928779, 14957787, 32615388, 70991040, 153985890, 335256886, 733206840, 1603258134, 3503385568, 7671749664, 16837946850
Offset: 0

Views

Author

Seiichi Manyama, Nov 18 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n\3, binomial(3*k, n-3*k)*binomial(2*k, k)/(k+1));

Formula

a(n) = Sum_{k=0..floor(n/3)} binomial(3*k,n-3*k) * C(k), where C(k) are the Catalan numbers (A000108).
G.f.: 2/(1 + sqrt(1 - 4*(x*(1+x))^3)).
Showing 1-8 of 8 results.