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 1-10 of 241 results. Next

A034943 Binomial transform of Padovan sequence A000931.

Original entry on oeis.org

1, 1, 1, 2, 5, 12, 28, 65, 151, 351, 816, 1897, 4410, 10252, 23833, 55405, 128801, 299426, 696081, 1618192, 3761840, 8745217, 20330163, 47261895, 109870576, 255418101, 593775046, 1380359512, 3208946545
Offset: 0

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Author

Keywords

Comments

Trisection of the Padovan sequence: a(n) = A000931(3n). - Paul Barry, Jul 06 2004
a(n+1) gives diagonal sums of Riordan array (1/(1-x),x/(1-x)^3). - Paul Barry, Oct 11 2005
a(n+2) is the sum, over all Boolean n-strings, of the product of the lengths of the runs of 1. For example, the Boolean 7-string (0,1,1,0,1,1,1) has two runs of 1s. Their lengths, 2 and 3, contribute a product of 6 to a(9). The 8 Boolean 3-strings contribute to a(5) as follows: 000 (empty product), 001, 010, 100, 101 all contribute 1, 011 and 110 contribute 2, 111 contributes 3. - David Callan, Nov 29 2007
[a(n), a(n+1), a(n+2)], n > 0, = [0,1,0; 0,0,1; 1,-2,3]^n * [1,1,1]. - Gary W. Adamson, Mar 27 2008
Without the initial 1 and 1: 1, 2, 5, 12, 28, this is also the transform of 1 by the T_{1,0} transformation; see Choulet link. - Richard Choulet, Apr 11 2009
Without the first 1: transform of 1 by T_{0,0} transformation (see Choulet link). - Richard Choulet, Apr 11 2009
Starting (1, 2, 5, 12, ...) = INVERT transform of (1, 1, 2, 3, 4, 5, ...) and row sums of triangle A159974. - Gary W. Adamson, Apr 28 2009
a(n+1) is also the number of 321-avoiding separable permutations. (A permutation is separable if it avoids both 2413 and 3142.) - Vince Vatter, Sep 21 2009
a(n+1) is an eigensequence of the sequence array for (1,1,2,3,4,5,...). - Paul Barry, Nov 03 2010
Equals the INVERTi transform of A055588: (1, 2, 4, 9, 22, 56, ...) - Gary W. Adamson, Apr 01 2011
The Ca3 sums, see A180662, of triangle A194005 equal the terms of this sequence without a(0) and a(1). - Johannes W. Meijer, Aug 16 2011
Without the initial 1, a(n) = row sums of A182097(n)*A007318(n,k); i.e., a Triangular array T(n,k) multiplying the binomial (Pascal's) triangle by the Padovan sequence where a(0) = 1, a(1) = 0 and a(2) = 1. - Bob Selcoe, Jun 28 2013
a(n+1) is the top left entry of the n-th power of any of the 3 X 3 matrices [1, 1, 1; 0, 1, 1; 1, 0, 1] or [1, 1, 0; 1, 1, 1; 1, 0, 1] or [1, 1, 1; 1, 1, 0; 0, 1, 1] or [1, 0, 1; 1, 1, 0; 1, 1, 1]. - R. J. Mathar, Feb 03 2014
a(n) is the top left entry of the n-th power of the 3 X 3 matrix [1, 0, 1; 1, 1, 1; 0, 1, 1] or of the 3 X 3 matrix [1, 1, 0; 0, 1, 1; 1, 1, 1]. - R. J. Mathar, Feb 03 2014
Number of sequences (e(1), ..., e(n-1)), 0 <= e(i) < i, such that there is no triple i < j < k with e(i) != e(j) < e(k) and e(i) <= e(k). [Martinez and Savage, 2.8] - Eric M. Schmidt, Jul 17 2017
a(n+1) is the number of words of length n over the alphabet {0,1,2} that do not contain the substrings 01 or 12 and do not start with a 2 and do not end with a 0. - Yiseth K. Rodríguez C., Sep 11 2020

Examples

			G.f. = 1 + x + x^2 + 2*x^3 + 5*x^4 + 12*x^5 + 28*x^6 + 65*x^7 + 151*x^8 + ...
		

Crossrefs

Programs

  • Magma
    [n le 3 select 1 else 3*Self(n-1)-2*Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 14 2012
    
  • Maple
    A034943 := proc(n): add(binomial(n+k-1, 3*k), k=0..floor(n/2)) end: seq(A034943(n), n=0..28); # Johannes W. Meijer, Aug 16 2011
  • Mathematica
    LinearRecurrence[{3,-2,1},{1,1,1},30] (* Harvey P. Dale, Aug 11 2017 *)
  • PARI
    {a(n) = if( n<1, n = 0-n; polcoeff( (1 - x + x^2) / (1 - 2*x + 3*x^2 - x^3) + x * O(x^n), n), n = n-1; polcoeff( (1 - x + x^2) / (1 - 3*x + 2*x^2 - x^3) + x * O(x^n), n))} /* Michael Somos, Mar 31 2012 */
    
  • SageMath
    @CachedFunction
    def a(n): # a = A034943
        if (n<3): return 1
        else: return 3*a(n-1) - 2*a(n-2) + a(n-3)
    [a(n) for n in range(51)] # G. C. Greubel, Apr 22 2023

Formula

a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3).
a(n) = Sum_{k=0..floor(n/2)} binomial(n+k-1, 3*k). - Paul Barry, Jul 06 2004
G.f.: (1 - 2*x)/(1 - 3*x + 2*x^2 - x^3). - Paul Barry, Jul 06 2005
G.f.: 1 + x / (1 - x / (1 - x / (1 - x / (1 + x / (1 - x))))). - Michael Somos, Mar 31 2012
a(-1 - n) = A185963(n). - Michael Somos, Mar 31 2012
a(n) = A095263(n) - 2*A095263(n-1). - G. C. Greubel, Apr 22 2023

Extensions

Edited by Charles R Greathouse IV, Apr 20 2010

A133034 First differences of Padovan sequence A000931.

Original entry on oeis.org

-1, 0, 1, -1, 1, 0, 0, 1, 0, 1, 1, 1, 2, 2, 3, 4, 5, 7, 9, 12, 16, 21, 28, 37, 49, 65, 86, 114, 151, 200, 265, 351, 465, 616, 816, 1081, 1432, 1897, 2513, 3329, 4410, 5842, 7739, 10252, 13581, 17991, 23833, 31572, 41824, 55405, 73396
Offset: 0

Views

Author

Omar E. Pol, Nov 05 2007

Keywords

Crossrefs

The following are basically all variants of the same sequence: A000931, A078027, A096231, A124745, A133034, A134816, A164001, A182097, A228361 and probably A020720. However, each one has its own special features and deserves its own entry.
Cf. A002026.

Programs

  • Mathematica
    LinearRecurrence[{0,1,1},{-1,0,1},60] (* Harvey P. Dale, Dec 14 2013 *)

Formula

a(n+4) = A000931(n).
G.f.: ( 1-2*x^2 ) / ( -1+x^2+x^3 ). - R. J. Mathar, Sep 11 2011
a(n) = a(n-2) + a(n-3) with a(0) = -1, a(1) = 0, a(2) = 1. - Taras Goy, Mar 24 2019

A012781 Take every 5th term of Padovan sequence A000931, beginning with the second term.

Original entry on oeis.org

0, 1, 4, 16, 65, 265, 1081, 4410, 17991, 73396, 299426, 1221537, 4983377, 20330163, 82938844, 338356945, 1380359512, 5631308624, 22973462017, 93722435101, 382349636061, 1559831901918, 6363483400447, 25960439030624
Offset: 0

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Author

Keywords

Comments

Number of nonisomorphic graded posets with 0 and uniform hasse graph of rank n, with exactly 2 elements of each rank level above 0, for n > 0. (Uniform used in the sense of Retakh, Serconek and Wilson.) Here, we do not assume all maximal elements have maximal rank and thus use graded poset to mean: For every element x, all maximal chains among those with x as greatest element have the same finite length. - David Nacin, Feb 13 2012

References

  • R. Stanley, Enumerative combinatorics, Vol. 1, Cambridge University Press, Cambridge, 1997, pp. 96-100.

Programs

  • Magma
    I:=[0, 1, 4 ]; [n le 3 select I[n] else 5*Self(n-1)-4*Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 03 2012
    
  • Mathematica
    LinearRecurrence[{5, -4, 1}, {0, 1, 4}, 25] (* Harvey P. Dale, Jan 10 2012 *)
  • Python
    def a(n, adict={0:0, 1:1, 2:4}):
        if n in adict:
            return adict[n]
        adict[n]=5*a(n-1) - 4*a(n-2) + a(n-3)
        return adict[n] # David Nacin, Feb 27 2012

Formula

a(n+3) = 5*a(n+2) - 4*a(n+1) + a(n).
G.f.: x*(1-x)/(1-5*x+4*x^2-x^3). - Colin Barker, Feb 03 2012

Extensions

Initial term 0 added by Colin Barker, Feb 03 2012

A012814 Take every 5th term of Padovan sequence A000931, beginning with the third term.

Original entry on oeis.org

0, 1, 5, 21, 86, 351, 1432, 5842, 23833, 97229, 396655, 1618192, 6601569, 26931732, 109870576, 448227521, 1828587033, 7459895657, 30433357674, 124155792775, 506505428836, 2066337330754, 8429820731201, 34390259761825, 140298353215075, 572360547759276, 2334999585697905
Offset: 0

Views

Author

Keywords

Examples

			G.f. = x + 5*x^2 + 21*x^3 + 86*x^4 + 351*x^5 + 1432*x^6 + 5842*x^7 + ...
		

Crossrefs

Programs

  • Magma
    I:=[0, 1, 5 ]; [n le 3 select I[n] else 5*Self(n-1)-4*Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 03 2012
  • Mathematica
    LinearRecurrence[{5, -4, 1}, {0, 1, 5}, 25] (* Vincenzo Librandi, Feb 03 2012 *)

Formula

a(n+3) = 5*a(n+2) - 4*a(n+1) + a(n).
a(n) = A000931(5*n+2).
G.f.: x/(1-5*x+4*x^2-x^3). - Colin Barker, Feb 03 2012
a(n) = A012855(n+4) - A012855(n+3).

Extensions

Initial term 0 added by Colin Barker, Feb 03 2012

A139038 Triangle read by rows: T(n,m) = A000931(m+6) if m <= floor(n/2), A000931(n+6-m) otherwise, for 0 <= m <= n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 2, 2, 3, 2, 2, 1, 1, 1, 1, 2, 2, 3, 3, 2, 2, 1, 1, 1, 1, 2, 2, 3, 4, 3, 2, 2, 1
Offset: 0

Views

Author

Roger L. Bagula and Gary W. Adamson, May 31 2008

Keywords

Comments

The Padovan sequence is pushed back to a(-1)=1, so that the triangle is not almost all ones.

Examples

			The triangle begins:
  1;
  1, 1;
  1, 1, 1;,
  1, 1, 1, 1;
  1, 1, 2, 1, 1;
  1, 1, 2, 2, 1, 1;
  1, 1, 2, 2, 2, 1, 1;
  1, 1, 2, 2, 2, 2, 1, 1;
  1, 1, 2, 2, 3, 2, 2, 1, 1;
  1, 1, 2, 2, 3, 3, 2, 2, 1, 1;
  1, 1, 2, 2, 3, 4, 3, 2, 2, 1, 1;
  ...
		

Crossrefs

Programs

  • Mathematica
    a[-1] = 1; a[0] = 1; a[1] = 1; a[n_] := a[n] = a[n - 2] + a[n - 3]; (* Padovan : A000931 *)
    Table[If[m <= Floor[n/2], a[m], a[n - m]], {n, 0, 10}, {m, 0, n}]

Extensions

Edited by N. J. A. Sloane, Feb 28 2009
Non-ASCII characters in %t line corrected by Wouter Meeussen, Feb 10 2013
Definition corrected and offset changed by Georg Fischer, May 16 2024

A144400 Triangle read by rows: row n (n > 0) gives the coefficients of x^k (0 <= k <= n - 1) in the expansion of Sum_{j=0..n} A000931(j+4)*binomial(n, j)*x^(j - 1)*(1 - x)^(n - j).

Original entry on oeis.org

1, 2, -1, 3, -3, 1, 4, -6, 4, 0, 5, -10, 10, 0, -3, 6, -15, 20, 0, -18, 10, 7, -21, 35, 0, -63, 70, -24, 8, -28, 56, 0, -168, 280, -192, 49, 9, -36, 84, 0, -378, 840, -864, 441, -89, 10, -45, 120, 0, -756, 2100, -2880, 2205, -890, 145, 11, -55, 165, 0
Offset: 1

Views

Author

Roger L. Bagula and Gary W. Adamson, Oct 03 2008

Keywords

Examples

			Triangle begins:
    1;
    2,  -1;
    3,  -3,   1;
    4,  -6,   4, 0;
    5, -10,  10, 0,   -3;
    6, -15,  20, 0,  -18,   10;
    7, -21,  35, 0,  -63,   70,   -24;
    8, -28,  56, 0, -168,  280,  -192,   49;
    9, -36,  84, 0, -378,  840,  -864,  441,  -89;
   10, -45, 120, 0, -756, 2100, -2880, 2205, -890, 145;
     ... reformatted. - _Franck Maminirina Ramaharo_, Oct 22 2018
		

Crossrefs

Programs

  • Mathematica
    a[n_]:= a[n]= If[n<3, Fibonacci[n], a[n-2] + a[n-3]];
    p[x_, n_]:= Sum[a[k]*Binomial[n, k]*x^(k-1)*(1-x)^(n-k), {k, 0, n}];
    Table[Coefficient[p[x, n], x, k], {n, 12}, {k, 0, n-1}]//Flatten
  • Sage
    @CachedFunction
    def f(n): return fibonacci(n) if (n<3) else f(n-2) + f(n-3)
    def p(n,x): return sum( binomial(n,j)*f(j)*x^(j-1)*(1-x)^(n-j) for j in (0..n) )
    def T(n): return ( p(n,x) ).full_simplify().coefficients(sparse=False)
    [T(n) for n in (1..12)] # G. C. Greubel, Jul 14 2021

Formula

G.f.: (y - (1 - 2*x)*y^2)/(1 - 3*(1 - x)*y + (3 - 6*x + 2*x^2)*y^2 - (1 - 3*x + 2*x^2 + x^3)*y^3). - Franck Maminirina Ramaharo, Oct 22 2018

Extensions

Edited, and new name by Franck Maminirina Ramaharo, Oct 22 2018

A100538 Volume of the 3-dimensional box of sides of length equal to consecutive Padovan numbers (A000931). These boxes form a spiral in three dimensions similar to the spiral of Fibonacci boxes in two dimensions.

Original entry on oeis.org

1, 2, 4, 12, 24, 60, 140, 315, 756, 1728, 4032, 9408, 21756, 50764, 117845, 273910, 637260, 1480404, 3442800, 8003000, 18603000, 43251975, 100540440, 233735040, 543371136, 1263161472, 2936540824, 6826574552, 15869878969, 36893076570
Offset: 1

Views

Author

John Lien, Nov 27 2004

Keywords

Comments

a(n)^(1/3) rounded to the nearest integer equals A000931(n+5). - Peter M. Chema, Apr 24 2017

Crossrefs

Cf. A000931.

Programs

  • Mathematica
    LinearRecurrence[{1, 2, 3, -2, 4, -4, -1, -1, 0, -1}, {1, 2, 4, 12, 24, 60, 140, 315, 756, 1728}, 50] (* Vincenzo Librandi, Apr 24 2017 *)

Formula

For large n a(n+1) -> a(n) * p^3 where p is the plastic number = 1.324718... a(n+1) = a(n)+ (a(n)/P(n))*P(n+1 ) where P are the Padovan numbers (A000931) starting 1, 1, 1, 2, 2, 3, 4, 5, 7, etc.
a(n) = +a(n-1) +2*a(n-2) +3*a(n-3) -2*a(n-4) +4*a(n-5) -4*a(n-6) -a(n-7) -a(n-8) -a(n-10) = A000931(n+4)*A000931(n+5)*A000931(n+6). G.f.: x*(1+x+x^3) / ( (x-1)*(x^3-2*x^2+3*x-1)*(x^6+3*x^5+5*x^4+5*x^3+5*x^2+3*x+1) ). - R. J. Mathar, Sep 14 2010

Extensions

More terms from R. J. Mathar, Sep 14 2010

A133037 a(n) = A000931(n)^2.

Original entry on oeis.org

1, 0, 0, 1, 0, 1, 1, 1, 4, 4, 9, 16, 25, 49, 81, 144, 256, 441, 784, 1369, 2401, 4225, 7396, 12996, 22801, 40000, 70225, 123201, 216225, 379456, 665856, 1168561, 2050624, 3598609, 6315169, 11082241, 19448100, 34128964, 59892121, 105103504, 184443561, 323676081
Offset: 0

Views

Author

Omar E. Pol, Nov 02 2007

Keywords

Comments

a(n+3) is the number of tilings of an n-board (a board with dimensions n X 1) with (1/2,1/2;2)-combs and (1/2,1/2;3)-combs. A (w,g;m)-comb is a tile composed of m pieces of dimensions w X 1 separated horizontally by gaps of width g. - Michael A. Allen, Sep 25 2024

Examples

			a(10)=9 because Padovan(10)=3 and 3^2=9.
		

Crossrefs

Cf. A000290, A001248, A007598. Padovan sequence: A000931.

Programs

  • Mathematica
    a[0] = a[3] = a[5] = a[6] = 1; a[1] = a[2] = a[4] = 0; a[n_Integer] := a[n] = 2*a[n - 2] + 2*a[n - 3] - a[n - 7]; Table[a[i], {i, 0, 40}] (* Olivier Gérard, Jul 05 2011 *)
    Table[RootSum[-1 - # + #^3 &, #^n (5 - 6 # + 4 #^2) &]^2/529, {n, 0,
    40}] (* Eric W. Weisstein, Apr 16 2018 *)
    LinearRecurrence[{1, 1, 1, -1, 1, -1}, {1, 0, 0, 1, 0, 1}, 40] (* Eric W. Weisstein, Apr 16 2018 *)
  • PARI
    Vec(O(x^20)+(1-x-x^2-x^5)/(1-x-x^2-x^3+x^4-x^5+x^6)) \\ Charles R Greathouse IV, Jul 05 2011

Formula

a(n) = A000931(n)^2.
a(n) = a(n-1) + a(n-2) + a(n-3) - a(n-4) + a(n-5) - a(n-6).
G.f.: (x^5+x^2+x-1)/(-x^6+x^5-x^4+x^3+x^2+x-1).
a(n) = a(n-2) + a(n-3) + 2*Sum_{r=8..n} ( A000930(r-8)*a(n+3-r) ) for n >= 3. - Michael A. Allen, Sep 25 2024

A134732 Concatenation of first n members of the Padovan sequence A000931, starting at (1, 1, 1, 2,).

Original entry on oeis.org

1, 11, 111, 1112, 11122, 111223, 1112234, 11122345, 111223457, 1112234579, 111223457912, 11122345791216, 1112234579121621, 111223457912162128, 11122345791216212837, 1112234579121621283749, 111223457912162128374965
Offset: 1

Views

Author

Omar E. Pol, Nov 10 2007

Keywords

Crossrefs

Cf. A000931, A007908, A019523, A102397. See A132347 for another version.

Programs

  • Mathematica
    Module[{nn=20,padseq},padseq=LinearRecurrence[{0,1,1},{1,1,1,2},nn];Table[ FromDigits[ Flatten[IntegerDigits/@Take[padseq,n]]],{n,nn}]] (* Harvey P. Dale, Feb 18 2023 *)

A329227 Products of consecutive terms of the Padovan sequence A000931.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 1, 2, 4, 6, 12, 20, 35, 63, 108, 192, 336, 588, 1036, 1813, 3185, 5590, 9804, 17214, 30200, 53000, 93015, 163215, 286440, 502656, 882096, 1547992, 2716504, 4767161, 8365777, 14680890, 25763220, 45211238, 79340228, 139232412, 244335771
Offset: 0

Views

Author

David Nacin, Nov 08 2019

Keywords

Examples

			For n=5, a(5) = A000931(5)*A000931(6) = 1*1.
		

Crossrefs

Programs

  • Mathematica
    Times@@@Partition[LinearRecurrence[{0,1,1},{1,0,0},50],2,1] (* Harvey P. Dale, Jul 05 2021 *)
  • Python
    p = lambda x:[1,0,0][x] if x<3 else p(x-2)+p(x-3)
    a = lambda x:p(x)*p(x+1)

Formula

a(n) = A000931(n)*A000931(n+1).
a(n+2) = Sum_{i=0..n} A000931(i)*A000931(i+2).
a(n) - a(n-2) - a(n-3) - a(n-4) = A133037(n-2) + A133037(n-3) for n>3.
G.f.: x^5 / ((1 - 2*x + x^2 - x^3)*(1 + x - x^3)) (conjectured). - Colin Barker, Nov 08 2019
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