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 1-5 of 5 results.

A011656 A binary m-sequence: expansion of reciprocal of x^3 + x^2 + 1 (mod 2), shifted by 2 initial 0's.

Original entry on oeis.org

0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1
Offset: 0

Views

Author

Keywords

Comments

Period 7.

References

  • S. W. Golomb, Shift-Register Sequences, Holden-Day, San Francisco, 1967.
  • H. D. Lueke, Korrelationssignale, Springer 1992, pp. 43-48.
  • F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier/North Holland, 1978, p. 408.

Crossrefs

Cf. A077962.
Cf. A011655..A011751 for other binary m-sequences.

Programs

  • Mathematica
    PadLeft[ Mod[ CoefficientList[ Series[1/(1 + x^2 + x^3), {x, 0, 102}], x], 2], 105] (* Robert G. Wilson v *)
  • PARI
    A011656_vec(N)=concat([0,0],Vec(lift(O(x^(N-1))+Mod(1,2)/(1+x^2+x^3))))
    A011656(n)=(n%7>3)||(n%7==2) \\ Faster than polcoeff(.../(1+x^2+x^3),n-2). - M. F. Hasler, Feb 17 2018

Formula

G.f.: (x^6 + x^5 + x^4 + x^2)/(1-x^7). a(n+7) = a(n). - Ralf Stephan, Aug 05 2013
G.f.: x^2/(1 + x^2 + x^3) in GF(2). - M. F. Hasler, Feb 16 2018

A219977 Expansion of 1/(1+x+x^2+x^3).

Original entry on oeis.org

1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0, 1, -1, 0, 0
Offset: 0

Views

Author

Harvey P. Dale, Dec 02 2012

Keywords

Examples

			G.f. = 1 - x + x^4 - x^5 + x^8 - x^9 + x^12 - x^13 + x^16 - x^17 + x^20 - x^21 + ...
		

Crossrefs

Programs

  • Magma
    m:=100; R:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/(1+x+x^2+x^3))); // Vincenzo Librandi, Apr 22 2015
  • Mathematica
    CoefficientList[Series[1/(1+x+x^2+x^3),{x,0,80}],x] (* or *) PadRight[{},120,{1,-1,0,0}]
    LinearRecurrence[{-1,-1,-1},{1,-1,0},80] (* Harvey P. Dale, May 22 2021 *)
  • PARI
    {a(n) = [1, -1, 0, 0][n%4 + 1]} /* Michael Somos, Dec 12 2012 */
    
  • PARI
    Vec(1/(1+x+x^2+x^3) + O(x^100)) \\ Michel Marcus, Jan 28 2016
    

Formula

G.f.: 1/(1 +x +x^2 +x^3).
Euler transform of length 4 sequence [ -1, 0, 0, 1]. - Michael Somos, Dec 12 2012
a(n) = a(n+4) = -a(1-n). |a(n)| = A133872(n). REVERT transform is A036765. INVERT transform is A077962. - Michael Somos, Dec 12 2012
A038505(n+2) = p(-1) where p(x) is the unique degree-n polynomial such that p(k) = a(k) for k = 0, 1, ..., n. - Michael Somos, Dec 12 2012
From Wesley Ivan Hurt, Apr 22 2015: (Start)
a(n) +a(n-1) +a(n-2) +a(n-3) = 0.
a(n) = (-1)^n/2 +(-1)^(n/2 +1/4 -(-1)^n/4)/2. (End)

A112455 a(n) = -a(n-2) - a(n-3).

Original entry on oeis.org

-3, 0, 2, 3, -2, -5, -1, 7, 6, -6, -13, 0, 19, 13, -19, -32, 6, 51, 26, -57, -77, 31, 134, 46, -165, -180, 119, 345, 61, -464, -406, 403, 870, 3, -1273, -873, 1270, 2146, -397, -3416, -1749, 3813, 5165, -2064, -8978, -3101, 11042, 12079, -7941
Offset: 0

Views

Author

Anthony C Robin, Dec 13 2005

Keywords

Comments

This sequence resembles the Perrin sequence, A001608. Like many such sequences with a(1)=0, any prime p divides a(p). The first pseudoprime (composite n divides a(n)) is 121.

Crossrefs

Programs

  • GAP
    a:=[-3,0,2];; for n in [4..60] do a[n]:=-a[n-2]-a[n-3]; od; a; # G. C. Greubel, May 19 2019
  • Magma
    I:=[-3,0,2]; [n le 3 select I[n] else -Self(n-2) -Self(n-3): n in [1..60]]; // G. C. Greubel, May 19 2019
    
  • Maple
    A112455 := proc(n)
        option remember ;
        if n <= 2 then
            op(n+1,[-3,0,2]) ;
        else
            -procname(n-2)-procname(n-3) ;
        end if;
    end proc: # R. J. Mathar, Feb 18 2024
  • Mathematica
    Table[ -Tr[MatrixPower[{{0, 0, -1}, {1, 0, -1}, {0, 1, 0}}, n]], {n, 1, 60}] (* Artur Jasinski, Jan 10 2007 *)
    LinearRecurrence[{0,-1,-1}, {-3,0,2}, 60] (* G. C. Greubel, May 19 2019 *)
  • PARI
    Vec(-(3+x^2)/(1+x^2+x^3)+O(x^60)) \\ Charles R Greathouse IV, May 15 2013
    
  • Sage
    (-(3+x^2)/(1+x^2+x^3)).series(x, 60).coefficients(x, sparse=False) # G. C. Greubel, May 19 2019
    

Formula

a(n) = - trace({{0, 0, -1}, {1, 0, -1}, {0, 1, 0}})^n. - Artur Jasinski, Jan 10 2007
From R. J. Mathar, Oct 24 2009: (Start)
G.f.: -(3+x^2)/(1+x^2+x^3).
a(n) = -3*A077962(n) - A077962(n-2). (End)
a(n) = (-1)^(n+1)*(A001609(n)^2 - A001609(2*n))/2. - Greg Dresden, Apr 14 2023

Extensions

Edited by Don Reble, Jan 25 2006

A077889 Expansion of 1/( (1-x)*(1 + x^2 + x^3) ).

Original entry on oeis.org

1, 1, 0, -1, 0, 2, 2, -1, -3, 0, 5, 4, -4, -8, 1, 13, 8, -13, -20, 6, 34, 15, -39, -48, 25, 88, 24, -112, -111, 89, 224, 23, -312, -246, 290, 559, -43, -848, -515, 892, 1364, -376, -2255, -987, 2632, 3243, -1644, -5874, -1598, 7519, 7473, -5920, -14991, -1552, 20912, 16544, -19359, -37455, 2816, 56815
Offset: 0

Views

Author

N. J. A. Sloane, Nov 17 2002

Keywords

Comments

The Gi1 sums, see A180662 for the definition of these sums, of triangle A101950 equal the terms of this sequence. - Johannes W. Meijer, Aug 06 2011

Crossrefs

Programs

  • GAP
    a:=[1,1,0,-1];; for n in [5..60] do a[n]:=a[n-1]-a[n-2]+a[n-4]; od; a; # G. C. Greubel, Dec 30 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 60); Coefficients(R!( 1/((1-x)*(1+x^2+x^3)) )); // G. C. Greubel, Dec 30 2019
    
  • Maple
    A101950 := proc(n,k) local j,k1: add((-1)^((n-j)/2)*binomial((n+j)/2,j)*(1+(-1)^(n+j))* binomial(j,k)/2, j=0..n) end: A077889 := proc(n): add(A101950(n-3*k,k), k=0..floor(n/4)) end: seq(A077889(n), n=0..60); # Johannes W. Meijer, Aug 06 2011
  • Mathematica
    CoefficientList[Series[1/((1-x)*(1+x^2+x^3)),{x,0,60}],x] (* or *) LinearRecurrence[{1,-1,0,1},{1,1,0,-1},60] (* Harvey P. Dale, Jul 14 2017 *)
  • PARI
    my(x='x+O('x^60)); Vec(1/((1-x)*(1+x^2+x^3))) \\ G. C. Greubel, Dec 30 2019
    
  • Sage
    def A077952_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( 1/((1-x)*(1+x^2+x^3)) ).list()
    A077952_list(60) # G. C. Greubel, Dec 30 2019
    

Formula

a(n) = Sum_{k=0..floor(n/4)} A101950(n-3*k, k).
a(n) = (1 + 2*A077962(n) + 2*A077962(n-1) + A077962(n-2))/3. - G. C. Greubel, Dec 30 2019
a(n)-a(n-1) = A077962(n). - R. J. Mathar, Mar 14 2021

A193736 Triangular array: the fusion of polynomial sequences P and Q given by p(n,x) = (n+1)-st Fibonacci polynomial and q(n,x) = (x+1)^n.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 4, 2, 1, 4, 8, 8, 3, 1, 5, 13, 19, 15, 5, 1, 6, 19, 36, 42, 28, 8, 1, 7, 26, 60, 91, 89, 51, 13, 1, 8, 34, 92, 170, 216, 182, 92, 21, 1, 9, 43, 133, 288, 446, 489, 363, 164, 34, 1, 10, 53, 184, 455, 826, 1105, 1068, 709, 290, 55, 1, 11, 64, 246, 682, 1414, 2219, 2619, 2266, 1362, 509, 89
Offset: 0

Views

Author

Clark Kimberling, Aug 04 2011

Keywords

Comments

See A193722 for the definition of fusion of two sequences of polynomials or triangular arrays.

Examples

			First six rows:
  1;
  1,  1;
  1,  2,  1;
  1,  3,  4,  2;
  1,  4,  8,  8,  3;
  1,  5, 13, 19, 15,  5;
		

Crossrefs

Cf. A000007, A005314 (diagonal sums), A052542 (row sums), A077962.

Programs

  • Magma
    function T(n,k) // T = A193736
      if k lt 0 or n lt 0 then return 0;
      elif n lt 3 then return Binomial(n,k);
      else return T(n-1, k) + T(n-1, k-1) + T(n-2, k-2);
      end if;
    end function;
    [T(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Oct 24 2023
    
  • Mathematica
    (* First program *)
    p[0, x_] := 1
    p[n_, x_] := Fibonacci[n + 1, x] /; n > 0
    q[n_, x_] := (x + 1)^n
    t[n_, k_] := Coefficient[p[n, x], x^(n - k)];
    t[n_, n_] := p[n, x] /. x -> 0;
    w[n_, x_] := Sum[t[n, k]*q[n - k + 1, x], {k, 0, n}]; w[-1, x_] := 1
    g[n_] := CoefficientList[w[n, x], {x}]
    TableForm[Table[Reverse[g[n]], {n, -1, z}]]
    Flatten[Table[Reverse[g[n]], {n, -1, z}]] (* A193736 *)
    TableForm[Table[g[n], {n, -1, z}]]
    Flatten[Table[g[n], {n, -1, z}]]          (* A193737 *)
    (* Second program *)
    T[n_, k_]:= T[n, k]= If[n<3, Binomial[n, k], T[n-1,k] +T[n-1,k-1] +T[n -2,k-2]];
    Table[T[n, k], {n,0,12}, {k,0,n}]//TableForm (* G. C. Greubel, Oct 24 2023 *)
  • SageMath
    def T(n,k): # T = A193736
        if (n<3): return binomial(n,k)
        else: return T(n-1,k) +T(n-1,k-1) +T(n-2,k-2)
    flatten([[T(n,k) for k in range(n+1)] for n in range(13)]) # G. C. Greubel, Oct 24 2023

Formula

T(0,0) = T(1,0) = T(1,1) = T(2,0) = T(2,2) = 1; T(n,k) = 0 if k<0 or k>n; T(n,k) = T(n-1,k) + T(n-1,k-1) + T(n-2,k-2). - Philippe Deléham, Feb 13 2020
From G. C. Greubel, Oct 24 2023: (Start)
T(n, k) = A193737(n, n-k).
T(n, n) = Fibonacci(n) + [n=0] = A324969(n+1).
T(n, n-1) = A029907(n).
Sum_{k=0..n} T(n, k) = A052542(n).
Sum_{k=0..n} (-1)^k * T(n, k) = A000007(n).
Sum_{k=0..floor(n/2)} T(n-k, k) = A005314(n) + [n=0].
Sum_{k=0..floor(n/2)} (-1)^k * T(n-k, k) = [n=0] + A077962(n-1). (End)
Showing 1-5 of 5 results.