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.

A291000 p-INVERT of (1,1,1,1,1,...), where p(S) = 1 - S - S^2 - S^3.

Original entry on oeis.org

1, 3, 9, 26, 74, 210, 596, 1692, 4804, 13640, 38728, 109960, 312208, 886448, 2516880, 7146144, 20289952, 57608992, 163568448, 464417728, 1318615104, 3743926400, 10630080640, 30181847168, 85694918912, 243312448256, 690833811712, 1961475291648, 5569190816256
Offset: 0

Views

Author

Clark Kimberling, Aug 22 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 = (1,1,1,1,1,...) = A000012, in some cases t(1,1,1,1,1,...) is a shifted version of the cited sequence:
p(S) t(1,1,1,1,1,...)
1 - S A000079
1 - S^2 A000079
1 - S^3 A024495
1 - S^4 A000749
1 - S^5 A139761
1 - S^6 A290993
1 - S^7 A290994
1 - S^8 A290995
1 - S - S^2 A001906
1 - S - S^3 A116703
1 - S - S^4 A290996
1 - S^3 - S^6 A290997
1 - S^2 - S^3 A095263
1 - S^3 - S^4 A290998
1 - 2 S^2 A052542
1 - 3 S^2 A002605
1 - 4 S^2 A015518
1 - 5 S^2 A163305
1 - 6 S^2 A290999
1 - 7 S^2 A291008
1 - 8 S^2 A291001
(1 - S)^2 A045623
(1 - S)^3 A058396
(1 - S)^4 A062109
(1 - S)^5 A169792
(1 - S)^6 A169793
(1 - S^2)^2 A024007
1 - 2 S - 2 S^2 A052530
1 - 3 S - 2 S^2 A060801
(1 - S)(1 - 2 S) A053581
(1 - 2 S)(1 - 3 S) A291002
(1 - S)(1 - 2 S)(1 - 3 S)(1 - 4 S) A291003
(1 - 2 S)^2 A120926
(1 - 3 S)^2 A291004
1 + S - S^2 A000045 (Fibonacci numbers starting with -1)
1 - S - S^2 - S^3 A291000
1 - S - S^2 - S^3 - S^4 A291006
1 - S - S^2 - S^3 - S^4 - S^5 A291007
1 - S^2 - S^4 A290990
(1 - S)(1 - 3 S) A291009
(1 - S)(1 - 2 S)(1 - 3 S) A291010
(1 - S)^2 (1 - 2 S) A291011
(1 - S^2)(1 - 2 S) A291012
(1 - S^2)^3 A291013
(1 - S^3)^2 A291014
1 - S - S^2 + S^3 A045891
1 - 2 S - S^2 + S^3 A291015
1 - 3 S + S^2 A136775
1 - 4 S + S^2 A291016
1 - 5 S + S^2 A291017
1 - 6 S + S^2 A291018
1 - S - S^2 - S^3 + S^4 A291019
1 - S - S^2 - S^3 - S^4 + S^5 A291020
1 - S - S^2 - S^3 + S^4 + S^5 A291021
1 - S - 2 S^2 + 2 S^3 A175658
1 - 3 S^2 + 2 S^3 A291023
(1 - 2 S^2)^2 A291024
(1 - S^3)^3 A291143
(1 - S - S^2)^2 A209917

Crossrefs

Programs

  • Mathematica
    z = 60; s = x/(1 - x); p = 1 - s - s^2 - s^3;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A000012 *)
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A291000 *)

Formula

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

A291219 p-INVERT of (0,1,0,1,0,1,...), where p(S) = 1 - S - S^3.

Original entry on oeis.org

1, 1, 3, 5, 11, 21, 42, 83, 163, 323, 635, 1255, 2473, 4880, 9625, 18985, 37451, 73869, 145715, 287421, 566954, 1118331, 2205947, 4351307, 8583091, 16930447, 33395857, 65874464, 129939569, 256310161, 505580371, 997274197, 1967156763, 3880282533, 7653987242
Offset: 0

Views

Author

Clark Kimberling, Aug 24 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 = (1,0,1,0,1,...) = A000035, in some cases t(1,0,1,0,1,...) is a shifted version of the indicated sequence.
p(S) t(1,0,1,0,1,...)
1 - S A000045 (Fibonacci numbers)
1 - S^2 A147600
1 - S^3 A291217
1 - S^5 A291218
1 - S - S^2 A289846
1 - S - S^3 A291219
1 - S - S^4 A291220
1 - S^3- S^6 A291221
1 - S^2- S^3 A291222
1 - S^3- S^4 A291223
1 - 2S A052542
1 - 3S A006190
(1 - S)^2 A239342
(1 - S)^3 A276129
(1 - S)^4 A291224
(1 - S)^5 A291225
(1 - S)^6 A291226
1 - S - 2 S^2 A291227
1 - 2 S - 2 S^2 A291228
1 - 3 S - 2 S^2 A060801
(1 - S)(1 - 2 S) A291229
(1 - S)(1 - 2 S)(1 - 3 S) A291230
(1 - S)(1 - 2 S)(1 - 3 S)( 1 - 4 S) A291231
(1 - 2 S)^2 A291264
(1 - 3 S)^2 A291232
1 - S - S^2 - S^3 A291233
1 - S - S^2 - S^3 - S^4 A291234
1 - S - S^2 - S^3 - S^4 - S^5 A291235
(1 - S)(1 - 3 S) A291236
(1 - S)(1 - 2S)( 1 - 4S) A291237
(1 - S)^2 (1 - 2S) A291238
(1 - S^2) (1 - 2S) A291239
(1 - S^3)^2 A291240
1 - S - S^2 + S^3 A291241
1 - 2 S - S^2 + S^3 A291242
1 - 3 S + S^2 A291243
1 - 4 S + S^2 A291244
1 - 5 S + S^2 A291245
1 - 6 S + S^2 A291246
1 - S - S^2 - S^3 + S^4 A291247
1 - S - S^2 - S^3 - S^4 + S^5 A291248
1 - S - S^2 - S^3 + S^4 + S^5 A291249
1 - S - 2 S^2 + 2 S^3 A291250
1 - 3 S^2 + 2 S^3 A291251 (includes negative terms)
(1 - S^3)^3 A291252
(1 - S - S^2)^2 A291253
(1 - 2 S - S^2)^2 A291254
(1 - S - 2 S^2)^2 A291255

Crossrefs

Programs

  • Magma
    I:=[1,1,3,5,11,21]; [n le 6 select I[n] else Self(n-1)+3*Self(n-2)-Self(n-3)-3*Self(n-4)+Self(n-5)+Self(n-6): n in [1..45]]; // Vincenzo Librandi, Aug 25 2017
  • Mathematica
    z = 60; s = x/(1 - x^2); p = 1 - s - s^3;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A000035 *)
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A291219 *)
    LinearRecurrence[{1, 3, -1, -3, 1, 1}, {1, 1, 3, 5, 11, 21}, 50] (* Vincenzo Librandi, Aug 25 2017 *)

Formula

G.f.: -(1 - x^2 + x^4)/(-1 + x + 3*x^2 - x^3 - 3*x^4 + x^5 + x^6).
a(n) = a(n-1) + 3*a(n-2) - a(n-3) - 3*a(n-4) + a(n-5) + a(n-6) for n >= 7.

A220562 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly one horizontal or antidiagonal neighbor.

Original entry on oeis.org

1, 2, 1, 3, 5, 1, 5, 14, 13, 1, 8, 47, 64, 34, 1, 13, 149, 430, 292, 89, 1, 21, 481, 2604, 3966, 1332, 233, 1, 34, 1544, 16310, 45966, 36640, 6076, 610, 1, 55, 4965, 101052, 561636, 810778, 338581, 27716, 1597, 1, 89, 15957, 628269, 6743873, 19333688, 14298089
Offset: 1

Views

Author

R. H. Hardin Dec 16 2012

Keywords

Comments

Table starts
.1.....2........3............5...............8..................13
.1.....5.......14...........47.............149.................481
.1....13.......64..........430............2604...............16310
.1....34......292.........3966...........45966..............561636
.1....89.....1332........36640..........810778............19333688
.1...233.....6076.......338581........14298089...........665748170
.1...610....27716......3128843.......252139015.........22926570957
.1..1597...126428.....28913910......4446314533........789539775889
.1..4181...576708....267196106.....78407942556......27190037181789
.1.10946..2630684...2469184016...1382674335890.....936366170726784
.1.28657.12000004..22817958901..24382584703194...32246430390993213
.1.75025.54738652.210862878471.429971411669361.1110497486239608510

Examples

			Some solutions for n=3 k=4 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
..0..0..0..0....0..6..4..0....0..7..6..4....0..7..6..4....6..4..0..0
..0..7..6..4....6..4..7..0....3..0..0..0....3..0..0..7....6..4..7..7
..3..6..4..0....0..3..0..0....0..0..0..0....0..0..3..0....0..3..3..0
		

Crossrefs

Column 2 is A001519(n+1)
Column 3 is A060801
Row 1 is A000045(n+1)

A221828 T(n,k)=Number of nXk arrays of occupancy after each element moves to some horizontal, vertical or antidiagonal neighbor, without 2-loops or left turns.

Original entry on oeis.org

0, 0, 0, 0, 3, 0, 0, 16, 14, 0, 0, 73, 202, 64, 0, 0, 333, 2879, 2930, 292, 0, 0, 1519, 40983, 115417, 41618, 1332, 0, 0, 6929, 583419, 4715043, 4755445, 592601, 6076, 0, 0, 31607, 8304016, 192788993, 570066685, 194407111, 8434490, 27716, 0, 0, 144177
Offset: 1

Views

Author

R. H. Hardin Jan 26 2013

Keywords

Comments

Table starts
.0......0..........0............0.............0..............0.............0
.0......3.........16...........73...........333...........1519..........6929
.0.....14........202.........2879.........40983.........583419.......8304016
.0.....64.......2930.......115417.......4715043......192788993....7888216533
.0....292......41618......4755445.....570066685....68573607669.8233561918895
.0...1332.....592601....194407111...68489860450.24121109763712
.0...6076....8434490...7954432829.8224749361083
.0..27716..120053263.325446165881
.0.126428.1708776751
.0.576708
.0

Examples

			Some solutions for n=3 k=4
..0..1..1..0....1..2..1..1....1..1..0..2....0..2..0..1....1..1..1..1
..1..2..0..1....1..1..2..1....2..1..1..1....2..1..0..1....1..0..1..2
..2..1..2..1....0..0..1..1....1..1..1..0....1..2..1..1....1..1..2..0
		

Crossrefs

Column 2 is A060801(n-1)

Formula

Empirical for col 2: a(n) = 5*a(n-1) -2*a(n-2) for n>3
Empirical for row 2: a(k)=5*a(k-1)-2*a(k-2) for k>4

A181308 Triangle read by rows: T(n,k) is the number of 2-compositions of n having k columns with an odd sum (0<=k<=n). A 2-composition of n is a nonnegative matrix with two rows, such that each column has at least one nonzero entry and whose entries sum up to n.

Original entry on oeis.org

1, 0, 2, 3, 0, 4, 0, 16, 0, 8, 14, 0, 52, 0, 16, 0, 104, 0, 144, 0, 32, 64, 0, 460, 0, 368, 0, 64, 0, 616, 0, 1624, 0, 896, 0, 128, 292, 0, 3428, 0, 5056, 0, 2112, 0, 256, 0, 3456, 0, 14688, 0, 14528, 0, 4864, 0, 512, 1332, 0, 23132, 0, 53920, 0, 39488, 0, 11008, 0, 1024, 0
Offset: 0

Views

Author

Emeric Deutsch, Oct 13 2010

Keywords

Comments

The sum of entries in row n is A003480(n).
T(n,k) = 0 if n and k have opposite parities.
T(2n,0) = A060801(n).
Sum(k*T(n,k), k=0..n) = A181326(n).
For the statistic "number of column with an even sum" see A181327.

Examples

			T(2,2) = 4 because we have (1,0/0,1), (0,1/1,0), (1,1/0,0), and (0,0/1,1) (the 2-compositions are written as (top row/bottom row)).
Triangle starts:
1;
0,  2;
3,  0,  4;
0, 16,  0, 8;
14, 0, 52, 0, 16;
		

Crossrefs

Programs

  • Maple
    G := (1-z^2)^2/(1-5*z^2+2*z^4-2*t*z): Gser := simplify(series(G, z = 0, 15)): for n from 0 to 11 do P[n] := sort(coeff(Gser, z, n)) end do; for n from 0 to 11 do seq(coeff(P[n], t, k), k = 0 .. n) end do; # yields sequence in triangular form
    # second Maple program:
    b:= proc(n) option remember; `if`(n=0, 1,
           expand(add(add(`if`(i=0 and j=0, 0, b(n-i-j)*
           `if`(irem(i+j,2)=1, x, 1)), i=0..n-j), j=0..n)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n)):
    seq(T(n), n=0..15); # Alois P. Heinz, Mar 16 2014
  • Mathematica
    b[n_] := b[n] = If[n == 0, 1, Expand[Sum[Sum[If[i == 0 && j == 0, 0, b[n-i-j]* If[Mod[i+j, 2] == 1, x, 1]], {i, 0, n-j}], {j, 0, n}]]]; T[n_] := Function[{p}, Table[Coefficient[p, x, i], {i, 0, Exponent[p, x]}]][b[n]]; Table[T[n], {n, 0, 15}] // Flatten (* Jean-François Alcover, Feb 19 2015, after Alois P. Heinz *)

Formula

G.f.: G(t,z) = (1-z)^2*(1+z)^2/(1-5z^2+2z^4-2tz).
The g.f. of column k is (2z)^k*(1-z^2)^2/(1-5z^2+2z^4)^{k+1} (we have a Riordan array).
The g.f. H(t,s,z), where z marks size and t (s) marks number of columns with an odd (even) sum, is H=(1-z^2)^2/(1-2z^2+z^4-2tz-3sz^2+sz^4).

A292744 a(0) = 1; a(n) = Sum_{k=1..n} prime(k+1)*a(n-k).

Original entry on oeis.org

1, 3, 14, 64, 294, 1346, 6166, 28242, 129362, 592538, 2714096, 12431808, 56943398, 260826950, 1194707382, 5472309246, 25065693008, 114812401444, 525893599720, 2408834540066, 11033569993066, 50538824799712, 231491059896394, 1060335514811206, 4856824295820082, 22246488881086116
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 22 2017

Keywords

Comments

Invert transform of the odd primes.
Number of compositions (ordered partitions) of n where there are prime(k+1) sorts of part k.

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[n_] := a[n] = Sum[Prime[k + 1] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 25}]
    nmax = 25; CoefficientList[Series[1/(1 - Sum[Prime[k + 1] x^k, {k, 1, nmax}]), {x, 0, nmax}], x]
  • PARI
    t=26; Vec(1/(1-sum(k=1, t, prime(k+1)*x^k)) + O(x^t)) \\ Felix Fröhlich, Sep 22 2017

Formula

G.f.: 1/(1 - Sum_{k>=1} prime(k+1)*x^k).
Showing 1-6 of 6 results.