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.

Previous Showing 11-19 of 19 results.

A146078 Expansion of 1/(1-x*(1-9*x)).

Original entry on oeis.org

1, 1, -8, -17, 55, 208, -287, -2159, 424, 19855, 16039, -162656, -307007, 1156897, 3919960, -6492113, -41771753, 16657264, 392603041, 242687665, -3290739704, -5474928689, 24141728647, 73416086848, -143859470975, -804604252607
Offset: 0

Views

Author

Philippe Deléham, Oct 27 2008

Keywords

Comments

Row sums of Riordan array (1, x(1-9x)).

Crossrefs

Programs

  • Magma
    I:=[1,1]; [n le 2 select I[n] else Self(n-1) - 9*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 19 2018
  • Mathematica
    LinearRecurrence[{1, -9}, {1, 1}, 100] (* G. C. Greubel, Jan 30 2016 *)
  • PARI
    x='x+O('x^30); Vec(1/(1-x+9*x^2)) \\ G. C. Greubel, Jan 19 2018
    
  • Sage
    [lucas_number1(n,1,9) for n in range(1, 27)] # Zerinvary Lajos, Apr 22 2009
    

Formula

a(n) = a(n-1) - 9*a(n-2), a(0)=1, a(1)=1.
a(n) = Sum_{k=0..n} A109466(n,k)*9^(n-k).
From G. C. Greubel, Jan 31 2016: (Start)
G.f.: 1/(1-x+9*x^2).
E.g.f.: exp(x/2)*(cos(sqrt(35)*x/2) + (1/sqrt(35))*sin(sqrt(35)*x/2)). (End)
a(n) = Product_{k=1..n} (1 + 6*cos(k*Pi/(n+1))). - Peter Luschny, Nov 28 2019
a(n) = 3^n * U(n, 1/6), where U(n, x) is the Chebyshev polynomial of the second kind. - Federico Provvedi, Mar 28 2022

A214733 a(n) = -a(n-1) - 3*a(n-2) with n>1, a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, -1, -2, 5, 1, -16, 13, 35, -74, -31, 253, -160, -599, 1079, 718, -3955, 1801, 10064, -15467, -14725, 61126, -16951, -166427, 217280, 282001, -933841, 87838, 2713685, -2977199, -5163856, 14095453, 1396115, -43682474, 39494129, 91553293, -210035680
Offset: 0

Views

Author

Roman Witula, Jul 27 2012

Keywords

Comments

The sequence a(n) is conjugate with A110523 by the following alternative relations: either ((-1 + i*sqrt(11))/2)^n = A110523(n) + a(n)*(-1 + i*sqrt(11))/2, or ((-1 - i*sqrt(11))/2)^n = A110523(n) + a(n)*(-1 - i*sqrt(11))/2 (see also comments to A110523, where these relations and many other facts on a(n) is presented).
Apart from signs, the Lucas U(P=1,Q=3)-sequence. - R. J. Mathar, Oct 24 2012
This is the Lucas U(-1, 3) sequence. (V_n(-1, 3))^2 + 11*(U_n(-1, 3))^2 = 4*Q^n = 4*3^n. For the special case where |U_n(-1, 3)| = 1, then, by the Lucas sequence identity U_2*n = U_n*V_n, we have (U_2*n(-1, 3))^2 + 11 = 4*3^n, true for n = 1, 2, 5, U_n = 1, -1, 1 and U_2*n = -1, 5, -31. E.g., (-31)^2 + 11 = 972 = 4*3^5. - Raphie Frank, Dec 09 2015

References

  • Roman Witula, On Some Applications of Formulae for Unimodular Complex Numbers, Jacek Skalmierski's Press, Gliwice 2011.

Crossrefs

Programs

  • Magma
    [n le 2 select n-1 else -Self(n-1)-3*Self(n-2): n in [1..40]]; // Vincenzo Librandi, Dec 10 2015
    
  • Mathematica
    LinearRecurrence[{-1, -3}, {0, 1}, 40] (* T. D. Noe, Jul 30 2012 *)
  • PARI
    concat(0,Vec(1/(1+x+3*x^2)+O(x^99))) \\ Charles R Greathouse IV, Oct 01 2012
    
  • SageMath
    [(-1)^(n-1)*round(3^((n-1)/2)*chebyshev_U(n-1, 1/(2*sqrt(3)))) for n in range(41)] # G. C. Greubel, Dec 28 2023

Formula

a(n) = - a(n-1) - 3*a(n-2).
a(n) = (-1)^n*(i*sqrt(11)/11)*(((1 + i*sqrt(11))/2)^n - ((1 - i*sqrt(11))/2)^n).
G.f.: x/(1 + x + 3*x^2).
G.f.: Q(0) -1, where Q(k) = 1 - 3*x^2 - (k+2)*x + x*(k+1 + 3*x)/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, Oct 07 2013
From G. C. Greubel, Dec 28 2023: (Start)
a(n) = (-1)^(n-1)*3^((n-1)/2)*ChebyshevU(n-1, 1/(2*sqrt(3))).
a(n) = (-1)^n * A106852(n-1).
E.g.f.: (2/sqrt(11))*exp(-x/2)*sin(sqrt(11)*x/2). (End)

A146083 Expansion of 1/(1 - x*(1 - 11*x)).

Original entry on oeis.org

1, 1, -10, -21, 89, 320, -659, -4179, 3070, 49039, 15269, -524160, -692119, 5073641, 12686950, -43123101, -182679551, 291674560, 2301149621, -907270539, -26219916370, -16239940441, 272179139629, 450818484480, -2543152051439
Offset: 0

Views

Author

Philippe Deléham, Oct 27 2008

Keywords

Comments

Row sums of Riordan array (1,x(1-11x)).

Crossrefs

Programs

Formula

a(n) = a(n-1)-11*a(n-2) ; a(0)=1, a(1)=1.
a(n) = Sum_{k=0..n} A109466(n,k)*11^(n-k).
From G. C. Greubel, Jan 31 2016: (Start)
G.f.: 1/(1-x+11*x^2).
E.g.f.: exp(x/2)*(cos(sqrt(43)*x/2) + (1/sqrt(43))*sin(sqrt(43)*x/2)).
(End)

A146084 Expansion of 1/(1-x(1-12x)).

Original entry on oeis.org

1, 1, -11, -23, 109, 385, -923, -5543, 5533, 72049, 5653, -858935, -926771, 9380449, 20501701, -92063687, -338084099, 766680145, 4823689333, -4376472407, -62260744403, -9743075519, 737385857317, 854302763545, -7994327524259
Offset: 0

Views

Author

Philippe Deléham, Oct 27 2008

Keywords

Comments

Row sums of Riordan array (1,x(1-12x)).

Crossrefs

Programs

Formula

a(n) = a(n-1)-12*a(n-2), a(0)=1, a(1)=1.
a(n) = Sum_{k, 0<=k<=n} A109466(n,k)*12^(n-k).

A106855 Expansion of 1/(1-x^2(1-3x)).

Original entry on oeis.org

1, 0, 1, -3, 1, -6, 10, -9, 28, -39, 55, -123, 172, -288, 541, -804, 1405, -2427, 3817, -6642, 11098, -18093, 31024, -51387, 85303, -144459, 239464, -400368, 672841, -1118760, 1873945, -3137283, 5230225, -8759118, 14642074, -24449793, 40919428, -68376015, 114268807, -191134299, 319396852
Offset: 0

Views

Author

Paul Barry, May 08 2005

Keywords

Comments

Diagonal sums of Riordan array (1,x(1-3x)).

Crossrefs

Formula

G.f.: 1/(1-x^2+3x^3); a(n)=a(n-2)-3a(n-3); a(n)=sum{k=0..floor(n/2), (-1)^n*binomial(k, n-2k)*3^(n-2k)}.

A128100 Triangle read by rows: T(n,k) is the number of ways to tile a 2 X n rectangle with k pieces of 2 X 2 tiles and n-2k pieces of 1 X 2 tiles (0 <= k <= floor(n/2)).

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 5, 5, 1, 8, 10, 3, 13, 20, 9, 1, 21, 38, 22, 4, 34, 71, 51, 14, 1, 55, 130, 111, 40, 5, 89, 235, 233, 105, 20, 1, 144, 420, 474, 256, 65, 6, 233, 744, 942, 594, 190, 27, 1, 377, 1308, 1836, 1324, 511, 98, 7, 610, 2285, 3522, 2860, 1295, 315, 35, 1, 987, 3970
Offset: 0

Views

Author

Emeric Deutsch, Feb 18 2007

Keywords

Comments

Row sums are the Jacobsthal numbers (A001045). Column 0 yields the Fibonacci numbers (A000045); the other columns yield convolved Fibonacci numbers (A001629, A001628, A001872, A001873, etc.). Sum_{k=0..floor(n/2)} k*T(n,k) = A073371(n-2).
Triangle T(n,k), with zeros omitted, given by (1, 1, -1, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (0, 1, -1, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938. - Philippe Deléham, Jan 24 2012
Riordan array (1/(1-x-x^2), x^2/(1-x-x^2)), with zeros omitted. - Philippe Deléham, Feb 06 2012
Diagonal sums are A000073(n+2) (tribonacci numbers). - Philippe Deléham, Feb 16 2014
Number of induced subgraphs of the Fibonacci cube Gamma(n-1) that are isomorphic to the hypercube Q_k. Example: row n=4 is 5, 5, 1; indeed, the Fibonacci cube Gamma(3) is a square with an additional pendant edge attached to one of its vertices; it has 5 vertices (i.e., Q_0's), 5 edges (i.e., Q_1's) and 1 square (i.e., Q_2). - Emeric Deutsch, Aug 12 2014
Row n gives the coefficients of the polynomial p(n,x) defined as the numerator of the rational function given by f(n,x) = 1 + (x + 1)/f(n-1,x), where f(x,0) = 1. Conjecture: for n > 2, p(n,x) is irreducible if and only if n is a (prime - 2). - Clark Kimberling, Oct 22 2014

Examples

			Triangle starts:
   1;
   1;
   2,  1;
   3,  2;
   5,  5,  1;
   8, 10,  3;
  13, 20,  9,  1;
  21, 38, 22,  4;
From _Philippe Deléham_, Jan 24 2012: (Start)
Triangle (1, 1, -1, 0, 0, ...) DELTA (0, 1, -1, 0, 0, 0, ...) begins:
   1;
   1,  0;
   2,  1,  0;
   3,  2,  0,  0;
   5,  5,  1,  0,  0;
   8, 10,  3,  0,  0,  0;
  13, 20,  9,  1,  0,  0,  0;
  21, 38, 22,  4,  0,  0,  0,  0; (End)
From _Clark Kimberling_, Oct 22 2014: (Start)
Here are the first 4 polynomials p(n,x) as in Comment and generated by Mathematica program:
  1
  2 +  x
  3 + 2x
  5 + 5x + x^2. (End)
		

Crossrefs

Programs

  • Maple
    G:=1/(1-z-(1+t)*z^2): Gser:=simplify(series(G,z=0,19)): for n from 0 to 16 do P[n]:=sort(coeff(Gser,z,n)) od: for n from 0 to 16 do seq(coeff(P[n],t,j),j=0..floor(n/2)) od; # yields sequence in triangular form
  • Mathematica
    p[x_, n_] := 1 + (x + 1)/p[x, n - 1]; p[x_, 1] = 1;
    Numerator[Table[Factor[p[x, n]], {n, 1, 20}]]  (* Clark Kimberling, Oct 22 2014 *)

Formula

G.f.: 1/(1-z-(1+t)z^2).
Sum_{k=0..n} T(n,k)*x^k = A053404(n), A015447(n), A015446(n), A015445(n), A015443(n), A015442(n), A015441(n), A015440(n), A006131(n), A006130(n), A001045(n+1), A000045(n+1), A000012(n), A010892(n), A107920(n+1), A106852(n), A106853(n), A106854(n), A145934(n), A145976(n), A145978(n), A146078(n), A146080(n), A146083(n), A146084(n) for x = 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, and -13, respectively. - Philippe Deléham, Jan 24 2012
T(n,k) = T(n-1,k) + T(n-2,k) + T(n-2,k-1). - Philippe Deléham, Jan 24 2012
G.f.: T(0)/2, where T(k) = 1 + 1/(1 - (2*k+1+ x*(1+y))*x/((2*k+2+ x*(1+y))*x + 1/T(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Nov 06 2013
T(n,k) = Sum_{i=k..floor(n/2)} binomial(n-i,i)*binomial(i,k). See Corollary 3.3 in the Klavzar et al. link. - Emeric Deutsch, Aug 12 2014

A190959 a(n) = 3*a(n-1) - 5*a(n-2), with a(0)=0, a(1)=1.

Original entry on oeis.org

0, 1, 3, 4, -3, -29, -72, -71, 147, 796, 1653, 979, -5328, -20879, -35997, -3596, 169197, 525571, 730728, -435671, -4960653, -12703604, -13307547, 23595379, 137323872, 293994721, 195364803, -883879196, -3628461603, -6465988829, -1255658472, 28562968729
Offset: 0

Views

Author

Keywords

Comments

This is the Lucas U(P=3, Q=5) sequence. - R. J. Mathar, Oct 24 2012
a(n+2)/a(n+1) equals the continued fraction 3 - 5/(3 - 5/(3 - 5/(3 - ... - 5/3))) with n 5's. - Greg Dresden, Oct 06 2019

Crossrefs

Cf. A190958 (index to generalized Fibonacci sequences), A190970 (binomial transf.), A106852 (inv. bin. transf., shifted).

Programs

  • Magma
    I:=[0,1]; [n le 2 select I[n] else 3*Self(n-1) - 5*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 25 2018
  • Mathematica
    LinearRecurrence[{3,-5}, {0,1}, 50]
  • PARI
    x='x+O('x^30); concat([0], Vec(x/(1-3x+5*x^2))) \\ G. C. Greubel, Jan 25 2018
    

Formula

G.f.: x/(1 - 3*x + 5*x^2). - Philippe Deléham, Oct 11 2011
E.g.f.: 2*exp(3*x/2)*sin(sqrt(11)*x/2)/sqrt(11). - Stefano Spezia, Oct 06 2019

A115672 Coefficients of L-series for elliptic curve "35a3": y^2 + y = x^3 + x^2 - x.

Original entry on oeis.org

1, 0, 1, -2, -1, 0, 1, 0, -2, 0, -3, -2, 5, 0, -1, 4, 3, 0, 2, 2, 1, 0, -6, 0, 1, 0, -5, -2, 3, 0, -4, 0, -3, 0, -1, 4, 2, 0, 5, 0, -12, 0, -10, 6, 2, 0, 9, 4, 1, 0, 3, -10, 12, 0, 3, 0, 2, 0, 0, 2, 8, 0, -2, -8, -5, 0, -4, -6, -6, 0, 0, 0, 2, 0, 1, -4, -3, 0, -1, -4, 1, 0, 12, -2, -3, 0, 3, 0, -12, 0, 5, 12, -4, 0, -2, 0, -1, 0, 6, -2, 6
Offset: 1

Views

Author

Michael Somos, Jan 29 2006

Keywords

Examples

			q + q^3 - 2*q^4 - q^5 + q^7 - 2*q^9 - 3*q^11 - 2*q^12 + 5*q^13 - q^15 + ...
		

Crossrefs

Cf. A106852(n) = a(3^n).

Programs

  • PARI
    {a(n)=if( n<1, 0, ellak( ellinit([ 0, 1, 1, -1, 0]), n))} /* Michael Somos, Mar 03 2011 */
    
  • PARI
    {a(n) = local(A); if( n<1, 0, n--; A = x * O(x^n); polcoeff( (eta(x^5 + A) * eta(x^7 + A))^2 + x^2 * (eta(x + A) * eta(x^35 + A))^2, n))}
    
  • Sage
    def a(n):
        return EllipticCurve("35a3").an(n)  # Robin Visser, Sep 30 2023

Formula

a(n) is multiplicative with a(5^e) = (-1)^e, a(7^e) = 1, a(p^e) = a(p) * a(p^(e-1)) - p * a(p^(e-2)) otherwise.
Expansion of (eta(q^5) * eta(q^7))^2 + (eta(q) * eta(q^35))^2 in powers of q. Expansion of a newform level 35 weight 2 and trivial character.

A201947 Triangle T(n,k), read by rows, given by (1,1,-1,0,0,0,0,0,0,0,...) DELTA (1,-1,1,0,0,0,0,0,0,...) where DELTA is the operator defined in A084938.

Original entry on oeis.org

1, 1, 1, 2, 2, 0, 3, 5, 1, -1, 5, 10, 4, -2, -1, 8, 20, 12, -4, -4, 0, 13, 38, 31, -4, -13, -2, 1, 21, 71, 73, 3, -33, -11, 3, 1, 34, 130, 162, 34, -74, -42, 6, 6, 0, 55, 235, 344, 128, -146, -130, 0, 24, 3, -1
Offset: 0

Views

Author

Philippe Deléham, Dec 06 2011

Keywords

Comments

Row-reversed variant of A123585. Row sums: 2^n.

Examples

			Triangle begins:
1
1, 1
2, 2, 0
3, 5, 1, -1
5, 10, 4, -2, -1
8, 20, 12, -4, -4, 0
13, 38, 31, -4, -13, -2, 1
21, 71, 73, 3, -33, -11, 3, 1
34, 130, 162, 34, -74, -42, 6, 6, 0
55, 235, 344, 128, -146, -130, 0, 24, 3, -1
		

Crossrefs

Cf. Columns: A000045, A001629, A129707.
Diagonals: A010892, A099254, Antidiagonal sums: A158943.

Formula

G.f.: 1/(1-(1+y)*x+(y+1)*(y-1)*x^2).
T(n,0) = A000045(n+1).
T(n,k) = T(n-1,k) + T(n-1,k-1) + T(n-2,k) - T(n-2,k-2) with T(0,0)= 1 and T(n,k)= 0 if n
Sum_{k, 0<=k<=n} T(n,k)*x^k = (-1)^n*A090591(n), (-1)^n*A106852(n), A000007(n), A000045(n+1), A000079(n), A057083(n), A190966(n+1) for n = -3, -2, -1, 0, 1, 2, 3 respectively.
Sum_{k, 0<=k<=n} T(n,k)*x^(n-k) = A010892(n), A000079(n), A030195(n+1), A180222(n+2) for x = 0, 1, 2, 3 respectively.
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