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 1-9 of 9 results.

A191497 a(n+1) = 2*a(n) + A014017(n+5), a(0) = 0.

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 4, 8, 15, 30, 60, 120, 241, 482, 964, 1928, 3855, 7710, 15420, 30840, 61681, 123362, 246724, 493448, 986895, 1973790, 3947580, 7895160, 15790321, 31580642, 63161284, 126322568, 252645135
Offset: 0

Views

Author

Paul Curtz, Jun 03 2011

Keywords

Crossrefs

Programs

Formula

a(n+4) = 2^n - a(n).
a(n) = 2*a(n-1) - a(n-4) + 2*a(n-5).
a(4*n+4) = 16*a(4*n) + (-1)^n.
From R. J. Mathar, Jun 23 2011: (Start)
G.f.: -x^4 / ((2*x-1)*(x^4+1)).
a(n) = (2^n - (-1)^floor(n/4)*A133145(n))/17. (End)

A301712 Coordination sequence for node of type V1 in "usm" 2-D tiling (or net).

Original entry on oeis.org

1, 5, 10, 16, 22, 27, 33, 38, 43, 49, 53, 59, 65, 70, 77, 81, 86, 92, 96, 103, 108, 113, 120, 124, 130, 135, 139, 146, 151, 157, 163, 167, 173, 178, 183, 189, 194, 200, 206, 211, 216, 221, 226, 232, 238, 243, 249, 254, 259, 265, 269, 275, 281, 286, 293, 297, 302, 308, 312, 319, 324, 329, 336, 340
Offset: 0

Views

Author

N. J. A. Sloane, Mar 26 2018

Keywords

Comments

Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 30 2023

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Table 2.2.1, page 67, 2nd row, 2nd tiling.

Crossrefs

Cf. A301714.
Coordination sequences for the 20 2-uniform tilings in the order in which they appear in the Galebach catalog, together with their names in the RCSR database (two sequences per tiling): #1 krt A265035, A265036; #2 cph A301287, A301289; #3 krm A301291, A301293; #4 krl A301298, A298024; #5 krq A301299, A301301; #6 krs A301674, A301676; #7 krr A301670, A301672; #8 krk A301291, A301293; #9 krn A301678, A301680; #10 krg A301682, A301684; #11 bew A008574, A296910; #12 krh A301686, A301688; #13 krf A301690, A301692; #14 krd A301694, A219529; #15 krc A301708, A301710; #16 usm A301712, A301714; #17 krj A219529, A301697; #18 kre A301716, A301718; #19 krb A301720, A301722; #20 kra A301724, A301726.

Programs

  • Mathematica
    LinearRecurrence[{1,0,0,-1,2,-1,0,0,1,-1},{1,5,10,16,22,27,33,38,43,49,53},100] (* Paolo Xausa, Nov 16 2023 *)

Formula

G.f.: -(-x^10-4*x^9-5*x^8-6*x^7-7*x^6-8*x^5-7*x^4-6*x^3-5*x^2-4*x-1)/(x^10-x^9+x^6-2*x^5+x^4-x+1). - N. J. A. Sloane, Mar 29 2018
Equivalent conjecture: 5*a(n) = 27*n -b(n) -5*A014017(n-2) for n>0, where b(n) = 2,-1,1,-2,0 (5-periodic) for n>=1. - R. J. Mathar, Mar 30 2018

Extensions

a(11)-a(100) from Davide M. Proserpio, Mar 28 2018

A188510 Expansion of x*(1 + x^2)/(1 + x^4) in powers of x.

Original entry on oeis.org

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

Views

Author

Michael Somos, Apr 10 2011

Keywords

Examples

			G.f. = x + x^3 - x^5 - x^7 + x^9 + x^11 - x^13 - x^15 + x^17 + x^19 - x^21 + ...
		

Crossrefs

Programs

  • Magma
    m:=60; R:=PowerSeriesRing(Integers(), m); [0] cat Coefficients(R!(x*(1+x^2)/(1+x^4))); // G. C. Greubel, Aug 02 2018
  • Mathematica
    Table[KroneckerSymbol[-2, n], {n, 0, 104}] (* Wolfdieter Lang, May 30 2013 *)
    a[ n_] := Mod[n, 2] (-1)^Quotient[ n, 4]; (* Michael Somos, Apr 17 2015 *)
    CoefficientList[Series[x*(1+x^2)/(1+x^4), {x, 0, 60}], x] (* G. C. Greubel, Aug 02 2018 *)
    LinearRecurrence[{0,0,0,-1},{0,1,0,1},120] (* or *) PadRight[{},120,{0,1,0,1,0,-1,0,-1}] (* Harvey P. Dale, Jan 25 2023 *)
  • PARI
    {a(n) = (n%2) * (-1)^(n\4)};
    
  • PARI
    x='x+O('x^60); concat([0], Vec(x*(1+x^2)/(1+x^4))) \\ G. C. Greubel, Aug 02 2018
    

Formula

Euler transform of length 8 sequence [0, 1, 0, -2, 0, 0, 0, 1].
a(n) is multiplicative with a(2^e) = 0^e, a(p^e) = 1 if p == 1 or 3 (mod 8), a(p^e) = (-1)^e if p == 5 or 7 (mod 8).
G.f.: x * (1 - x^4)^2/((1 - x^2)*(1 - x^8)) = (x + x^3)/(1 + x^4).
a(-n) = -a(n) = a(n+4).
a(n+2) = A091337(n).
a(2*n) = 0, a(2*n+1) = A057077(n).
G.f.: x/(1 - x^2/(1 + 2*x^2/(1 - x^2))). - Michael Somos, Jan 03 2013
a(n) = ((-2)/n), where (k/n) is the Kronecker symbol. Period 8. See the Eric Weisstein link. - Wolfdieter Lang, May 29 2013
a(n) = A257170(n) unless n = 0.
From Jianing Song, Nov 14 2018: (Start)
a(n) = sqrt(2)*sin(Pi*n/2)*cos(Pi*n/4).
E.g.f.: sqrt(2)*sin(x/sqrt(2))*cosh(x/sqrt(2)).
Moebius transform of A002325.
a(n) = A091337(n)*A101455(n).
a(n) = ((-2)^(2*i+1)/n) for all integers i >= 0, where (k/n) is the Kronecker symbol. (End)
a(n) = A014017(n-1)+A014017(n-3). - R. J. Mathar, Dec 17 2024

A107849 Expansion of (1 + x)^2 / ((1 - x^2 - 2*x^3)*(1 + x^4)).

Original entry on oeis.org

1, 2, 2, 4, 5, 6, 12, 16, 25, 42, 58, 92, 141, 206, 324, 488, 737, 1138, 1714, 2612, 3989, 6038, 9212, 14016, 21289, 32442, 49322, 75020, 114205, 173662, 264244, 402072, 611569, 930562, 1415714, 2153700, 3276837, 4985126, 7584236, 11538800
Offset: 0

Views

Author

Creighton Dement, May 25 2005

Keywords

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1 + x)^2 / ((1 - x^2 - 2*x^3)*(1 + x^4)),{x,0,39}],x] (* James C. McMahon, Feb 19 2024 *)
  • PARI
    Vec((1 + x)^2 / ((1 - x^2 - 2*x^3)*(1 + x^4)) + O(x^45)) \\ Colin Barker, Apr 30 2019

Formula

a(n) = A052947(n+2) + A014017(n+6). - Ralf Stephan, Nov 30 2010
a(n) = a(n-2) + 2*a(n-3) - a(n-4) + a(n-6) + 2*a(n-7) for n>6. - Colin Barker, Apr 30 2019

A128130 Expansion of (1-x)/(1+x^4); period 8: repeat [1,-1,0,0,-1,1,0,0].

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, 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

Paul Barry, Feb 15 2007

Keywords

Crossrefs

Programs

  • Maple
    A128130 := proc(n)
        local m ;
        m := modp(n,8) ;
        op(1+m,[1,-1,0,0,-1,1,0,0]) ;
    end proc: # R. J. Mathar, Feb 24 2015
  • Mathematica
    CoefficientList[Series[(1-x)/(1+x^4),{x,0,100}],x]  (* Harvey P. Dale, Mar 28 2011 *)
  • Scheme
    (define (A128130 n) (list-ref '(1 -1 0 0 -1 1 0 0) (modulo n 8))) ;; Antti Karttunen, Aug 12 2017

Formula

a(n) = (sqrt(2)/4 + 1/2)*cos(3*Pi*n/4) - sqrt(2)*sin(3*Pi*n/4)/4 + (1/2 - sqrt(2)/4)*cos(Pi*n/4) - sqrt(2)*sin(Pi*n/4)/4; a(n) = Im(Sum_{k=0..n} i^(n-k+1)), i=sqrt(-1).
abs(a(n)) = A133872(n). - Wesley Ivan Hurt, Feb 23 2015
a(n) = A014017(n) - A014017(n-1). - R. J. Mathar, Feb 24 2015

Extensions

More terms from Antti Karttunen, Aug 12 2017

A102905 a(n) = A113655(Fibonacci(n+1)).

Original entry on oeis.org

3, 3, 2, 1, 5, 8, 15, 19, 36, 57, 89, 142, 233, 377, 612, 985, 1599, 2586, 4181, 6763, 10946, 17711, 28659, 46366, 75027, 121395, 196418, 317809, 514229, 832040, 1346271, 2178307, 3524580, 5702889, 9227465, 14930350, 24157817, 39088169
Offset: 0

Views

Author

Roger L. Bagula, Mar 16 2005

Keywords

Crossrefs

Programs

Formula

a(n) = f(Fibonacci(n+1)), where f(n) = n-2 if (n mod 3) = 0, f(n) = n+2 if (n mod 3) = 1, otherwise f(n) = n.
a(n) = A113655(Fibonacci(n+1)).
G.f.: (3-4*x^2-4*x^3+2*x^4+2*x^5+2*x^6-4*x^7-x^8+2*x^9) / ((1-x)*(1+x)*(1+x^2)*(1-x-x^2)*(1+x^4)). - Colin Barker, Dec 11 2012
a(n) = (1 + 3*(-1)^n)/4 + Fibonacci(n+1) + (3/2)*(-1)^floor(n/2) * (n mod 2) + A014017(n) + A014017(n-1) - A014017(n-2). - G. C. Greubel, Dec 09 2022

Extensions

Edited by G. C. Greubel, Dec 09 2022

A107854 G.f. x*(x^2+1)*(x^3-x-1)/((2*x^3+x^2-1)*(x^4+1)).

Original entry on oeis.org

0, 1, 1, 2, 3, 3, 5, 8, 11, 19, 29, 42, 67, 99, 149, 232, 347, 531, 813, 1226, 1875, 2851, 4325, 6600, 10027, 15251, 23229, 35306, 53731, 81763, 124341, 189224, 287867, 437907, 666317, 1013642, 1542131, 2346275, 3569413, 5430536, 8261963, 12569363
Offset: 0

Views

Author

Creighton Dement, May 25 2005

Keywords

Comments

The sequence A078028 is given by 1em[I* ]forzapseq and is from the same "batch" (i.e., corresponding to the same floretion and symmetry settings) as A107849, A107850, A107851, A107852, A107853 and (a(n)).
Floretion Algebra Multiplication Program, FAMP Code: 1dia[I]forzapseq[(.5i' + .5j' + .5'ki' + .5'kj')*(.5'i + .5'j + .5'ik' + .5'jk')], 1vesforzap = A000004

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[x(x^2+1)(x^3-x-1)/((2x^3+x^2-1)(x^4+1)),{x,0,50}],x] (* or *) LinearRecurrence[{0,1,2,-1,0,1,2},{0,1,1,2,3,3,5},50] (* Harvey P. Dale, Jun 21 2022 *)
  • PARI
    a(n)=([0,1,0,0,0,0,0; 0,0,1,0,0,0,0; 0,0,0,1,0,0,0; 0,0,0,0,1,0,0; 0,0,0,0,0,1,0; 0,0,0,0,0,0,1; 2,1,0,-1,2,1,0]^n*[0;1;1;2;3;3;5])[1,1] \\ Charles R Greathouse IV, Oct 03 2016

Formula

a(n) = A159284(n) + A014017(n+5).

A122056 Expansion of g.f. x^2/((1 - x)^4*(1 + x)*(1 + x^2)*(1 + x^4)).

Original entry on oeis.org

0, 0, 1, 3, 6, 10, 15, 21, 28, 36, 46, 58, 72, 88, 106, 126, 148, 172, 199, 229, 262, 298, 337, 379, 424, 472, 524, 580, 640, 704, 772, 844, 920, 1000, 1085, 1175, 1270, 1370, 1475, 1585, 1700, 1820, 1946, 2078, 2216, 2360, 2510, 2666, 2828, 2996, 3171, 3353, 3542, 3738
Offset: 0

Views

Author

Roger L. Bagula, Sep 13 2006

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 72); [0,0] cat Coefficients(R!( x^2/((1-x)^4*(1+x)*(1+x^2)*(1+x^4)) )); // G. C. Greubel, Dec 29 2022
    
  • Mathematica
    p[n_]:= p[n] = If[n<0, 1, Cancel[Simplify[(x^(n-1)*p[n-1]*p[n-8] + p[n-4]*p[n-5])/p[n-9]]]]; Table[Exponent[p[n], x], {n,0,30}]
    LinearRecurrence[{3,-3,1,0,0,0,0,1,-3,3,-1}, {0,0,1,3,6,10,15,21,28,36, 46,58,72}, 61] (* G. C. Greubel, Dec 29 2022 *)
  • SageMath
    def A122056_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( x^2/((1-x)^4*(1+x)*(1+x^2)*(1+x^4)) ).list()
    A122056_list(70) # G. C. Greubel, Dec 29 2022

Formula

a(n) = degree(p(n)) with p(n) = (x^(n-1)*p(n-1)*p(n-8) + p(n-4)*p(n-5))/p(n-9).
From Colin Barker, Oct 08 2019: (Start)
G.f.: x^2 / ((1-x)^4*(1+x)*(1+x^2)*(1+x^4)).
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-8) - 3*a(n-9) + 3*a(n-10) - a(n-11) for n > 10. (End)
a(n) = (1/192)*(4*n^3 +42*n^2 +80*n -63 +3*(-1)^n) + (1/32)*(i^n*(1 + (-1)^n) + i^(n+1)*(1-(-1)^n)) + (1/4)*(b(n) -b(n-1) -2*b(n-2) -2*b(n -3)), where b(n) = A014017(n). - G. C. Greubel, Dec 29 2022

Extensions

Edited by G. C. Greubel, Dec 29 2022

A186187 Period 8 sequence [ 2, 2, 1, 2, 4, 2, 1, 2, ...] except a(0) = 1.

Original entry on oeis.org

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

Views

Author

Michael Somos, Feb 14 2011

Keywords

Comments

Also continued fraction expansion of sqrt(2717)/38. - Bruno Berselli, Mar 07 2011

Examples

			1 + 2*x + x^2 + 2*x^3 + 4*x^4 + 2*x^5 + x^6 + 2*x^7 + 2*x^8 + 2*x^9 + ...
		

Programs

  • Magma
    [1] cat &cat[ [2, 1, 2, 4, 2, 1, 2, 2]: n in [1..13]];  // Bruno Berselli, Mar 07 2011
  • Mathematica
    PadRight[{1},108,{2,2,1,2,4,2,1,2}] (* Harvey P. Dale, Mar 22 2012 *)
  • PARI
    {a(n) = - (n==0) + [ 2, 2, 1, 2, 4, 2, 1, 2] [n%8 + 1]}
    
  • PARI
    {a(n) = polcoeff( (1 + x)^4 * (1 - x + x^2)^2 / (1 - x^8) + x * O(x^abs(n)), abs(n))}
    

Formula

Euler transform of length 8 sequence [ 2, -2, 2, 0, 0, -2, 0, 1].
Moebius transform is length 8 sequence [ 2, -1, 0, 3, 0, 0, 0, -2].
a(n) = 2 * b(n) where b() is multiplicative with b(2) = 1/2, b(4) = 2, b(2^e) = 1 if e>2, b(p^e) = 1 if p>2.
G.f.: (1 + x)^4 * (1 - x + x^2)^2 / (1 - x^8) = (1-x+x^2)^2*(1+x)^3 / ((1-x) *(1+x^2) *(1+x^4)). a(-n) = a(n). a(2*n + 1) = 2, a(4*n + 2) = 1, a(8*n + 4) = 4, a(8*n) = 2 except a(0) = 1.
a(n) = A056594(n)-A014017(n)+2 for n>0. - Bruno Berselli, Feb 15 2011
Showing 1-9 of 9 results.