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 1-3 of 3 results.

A290890 p-INVERT of the positive integers, where p(S) = 1 - S^2.

Original entry on oeis.org

0, 1, 4, 11, 28, 72, 188, 493, 1292, 3383, 8856, 23184, 60696, 158905, 416020, 1089155, 2851444, 7465176, 19544084, 51167077, 133957148, 350704367, 918155952, 2403763488, 6293134512, 16475640049, 43133785636, 112925716859, 295643364940, 774004377960
Offset: 0

Views

Author

Clark Kimberling, Aug 15 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).
Note that in A290890, s = (1,2,3,4,...); i.e., A000027(n+1) for n>=0, whereas in A290990, s = (0,1,2,3,4,...); i.e., A000027(n) for n>=0.
Guide to p-INVERT sequences using s = (1,2,3,4,5,...) = A000027:
p(S) t(1,2,3,4,5,...)
1 - S A001906
1 - S^2 A290890; see A113067 for signed version
1 - S^3 A290891
1 - S^4 A290892
1 - S^5 A290893
1 - S^6 A290894
1 - S^7 A290895
1 - S^8 A290896
1 - S - S^2 A289780
1 - S - S^3 A290897
1 - S - S^4 A290898
1 - S^2 - S^4 A290899
1 - S^2 - S^3 A290900
1 - S^3 - S^4 A290901
1 - 2S A052530; (1/2)*A052530 = A001353
1 - 3S A290902; (1/3)*A290902 = A004254
1 - 4S A003319; (1/4)*A003319 = A001109
1 - 5S A290903; (1/5)*A290903 = A004187
1 - 2*S^2 A290904; (1/2)*A290904 = A290905
1 - 3*S^2 A290906; (1/3)*A290906 = A290907
1 - 4*S^2 A290908; (1/4)*A290908 = A099486
1 - 5*S^2 A290909; (1/5)*A290909 = A290910
1 - 6*S^2 A290911; (1/6)*A290911 = A290912
1 - 7*S^2 A290913; (1/7)*A290913 = A290914
1 - 8*S^2 A290915; (1/8)*A290915 = A290916
(1 - S)^2 A290917
(1 - S)^3 A290918
(1 - S)^4 A290919
(1 - S)^5 A290920
(1 - S)^6 A290921
1 - S - 2*S^2 A290922
1 - 2*S - 2*S^2 A290923; (1/2)*A290923 = A290924
1 - 3*S - 2*S^2 A290925
(1 - S^2)^2 A290926
(1 - S^2)^3 A290927
(1 - S^3)^2 A290928
(1 - S)(1 - S^2) A290929
(1 - S^2)(1 - S^4) A290930
1 - 3 S + S^2 A291025
1 - 4 S + S^2 A291026
1 - 5 S + S^2 A291027
1 - 6 S + S^2 A291028
1 - S - S^2 - S^3 A291029
1 - S - S^2 - S^3 - S^4 A201030
1 - 3 S + 2 S^3 A291031
1 - S - S^2 - S^3 + S^4 A291032
1 - 6 S A291033
1 - 7 S A291034
1 - 8 S A291181
1 - 3 S + 2 S^3 A291031
1 - 3 S + 2 S^2 A291182
1 - 4 S + 2 S^3 A291183
1 - 4 S + 3 S^3 A291184

Examples

			(See the examples at A289780.)
		

Crossrefs

Cf. A000027, A113067, A289780, A113067 (signed version of same sequence).

Programs

  • Mathematica
    z = 60; s = x/(1 - x)^2; p = 1 - s^2;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A000027 *)
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A290890 *)

Formula

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

A113066 Expansion of (1 + x)^2/((1 + x + x^2)*(1 + 3*x + x^2)).

Original entry on oeis.org

1, -2, 4, -10, 27, -72, 189, -494, 1292, -3382, 8855, -23184, 60697, -158906, 416020, -1089154, 2851443, -7465176, 19544085, -51167078, 133957148, -350704366, 918155951, -2403763488, 6293134513, -16475640050, 43133785636, -112925716858, 295643364939, -774004377960
Offset: 0

Views

Author

Creighton Dement, Oct 13 2005

Keywords

Comments

Binomial transform gives signed version of A093040.
The positive sequence has g.f. (1 - x)^2/((1 - x + x^2)(1 - 3*x + x^2)) and a(n) = Sum_{k=0..n} binomial(n+k+1, n-k)*(1+(-1)^k)/2. - Paul Barry, Jul 06 2009
Floretion Algebra Multiplication Program, FAMP Code: 2basei[C*F]; C = - .5'j + .5'k - .5j' + .5k' - 'ii' - .5'ij' - .5'ik' - .5'ji' - .5'ki'; F = + .5'i + .5'ii' + .5'ij' + .5'ik'

References

  • C. Dement, Floretion Integer Sequences (work in progress).

Crossrefs

Programs

  • GAP
    a:=[1,-2,4,-10];; for n in [5..35] do a[n]:=-4*a[n-1]-5*a[n-2]-4*a[n-3]-a[n-4]; od; a; # Muniru A Asiru, Sep 11 2018
    
  • Magma
    I:=[1,-2,4,-10]; [n le 4 select I[n] else -4*Self(n-1)-5*Self(n-2)- 4*Self(n-3)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Sep 12 2018
  • Maple
    seq(coeff(series((1+x)^2/((1+x+x^2)*(1+3*x+x^2)),x,n+1), x, n), n = 0 .. 35); # Muniru A Asiru, Sep 11 2018
  • Mathematica
    LinearRecurrence[{-4, -5, -4, -1}, {1, -2, 4, -10}, 40] (* Vincenzo Librandi, Sep 12 2018 *)
    CoefficientList[Series[(1 + x)^2/((1 + x + x^2)*(1 + 3 x + x^2)), {x, 0, 50}], x] (* Stefano Spezia, Sep 12 2018 *)
  • PARI
    x='x+O('x^99); Vec((1+x)^2/((1+x+x^2)*(1+3*x+x^2))) \\ Altug Alkan, Sep 11 2018
    

Formula

a(n) + a(n+1) = (-1)^(n+1)*A109961(n+1).
a(n) + a(n+1) + a(n+2) = (-1)^n*A001906(n+2) = (-1)^n*F(2*n+4).
a(n) = A049347(n)/2 + (-1)^n*A001906(n+1)/2. - R. J. Mathar, Nov 10 2009
Lim_{n -> inf} a(n)/a(n-1) = -(1 + A001622). - A.H.M. Smeets, Sep 11 2018
a(n) = -4*a(n-1) - 5*a(n-2) - 4*a(n-3) - a(n-4). - Muniru A Asiru, Sep 11 2018

A285935 Square array a(n, m) read by antidiagonals whose g.f. is 1 / ((1-x)^2 * (1-y)^2 - x*y).

Original entry on oeis.org

1, 2, 2, 3, 5, 3, 4, 10, 10, 4, 5, 18, 26, 18, 5, 6, 30, 58, 58, 30, 6, 7, 47, 116, 153, 116, 47, 7, 8, 70, 214, 354, 354, 214, 70, 8, 9, 100, 371, 746, 931, 746, 371, 100, 9, 10, 138, 612, 1464, 2204, 2204, 1464, 612, 138, 10, 11, 185, 969, 2714, 4816, 5794
Offset: 0

Views

Author

Michael Somos, Jun 14 2017

Keywords

Examples

			a(n,m) 0   1   2   3
----+--- --- --- ---
0   |  1   2   3   4
1   |  2   5  10  18
2   |  3  10  26  58
3   |  4  18  58 153
		

Crossrefs

Programs

  • Mathematica
    a[n_, m_] := SeriesCoefficient[1/((1-x)^2*(1-y)^2-x*y), {x, 0, n}, {y, 0, m}];
    Table[a[n-m, m], {n, 0, 10}, {m, 0, n}] // Flatten (* Jean-François Alcover, Jun 15 2017 *)
  • PARI
    {a(n, m) = if( n<0 || m<0, 0, polcoeff( polcoeff( -1/(x*y-sqr(1-x-y+x*y))*(1+x*O(x^n))*(1+y*O(y^k)), n), m))};

Formula

G.f. Sum_{n>=0, m>=0} a(n, m) * x^n * y^m = 1 / ((1-x)^2 * (1-y)^2 - x*y).
T(n, k) := a(n-k, k) where 0 <= k <= n.
a(n, m) = a(m, n) = T(n+m, n), T(n, 0) = a(n, 0) = n+1, if n>=0, m>=0.
Row sums are (-1)^(n+1) * A113067(n+1).
T(n, 1) = A177787(n+1).
Showing 1-3 of 3 results.