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.

A047461 Numbers that are congruent to {1, 4} mod 8.

Original entry on oeis.org

1, 4, 9, 12, 17, 20, 25, 28, 33, 36, 41, 44, 49, 52, 57, 60, 65, 68, 73, 76, 81, 84, 89, 92, 97, 100, 105, 108, 113, 116, 121, 124, 129, 132, 137, 140, 145, 148, 153, 156, 161, 164, 169, 172, 177, 180, 185, 188, 193, 196, 201, 204, 209, 212, 217, 220, 225, 228, 233
Offset: 1

Views

Author

Keywords

Comments

Maximal number of squares that can be covered by a queen on an n X n chessboard. - Reinhard Zumkeller, Dec 15 2008

Crossrefs

Programs

  • GAP
    Filtered([1..250], n->n mod 8=1 or n mod 8 =4); # Muniru A Asiru, Jul 23 2018
    
  • Magma
    [4*n-3 - ((n+1) mod 2): n in [1..70]]; // G. C. Greubel, Mar 15 2024
    
  • Maple
    seq(coeff(series(factorial(n)*((8-exp(-x)+(8*x-7)*exp(x))/2), x,n+1),x,n),n=1..60); # Muniru A Asiru, Jul 23 2018
  • Mathematica
    Flatten[(#+{1,4})&/@(8Range[0,30])] (* or *) LinearRecurrence[ {1,1,-1},{1,4,9},60] (* Harvey P. Dale, Jun 18 2013 *)
    CoefficientList[ Series[(4x^2 + 3x + 1)/((x + 1) (x - 1)^2), {x, 0, 58}], x] (* Robert G. Wilson v, Jul 24 2018 *)
  • Maxima
    makelist(4*n -(7 + (-1)^n)/2, n, 1, 100); /* Franck Maminirina Ramaharo, Jul 22 2018 */
    
  • Python
    def A047461(n): return (n-1<<2)|(n&1) # Chai Wah Wu, Mar 30 2024
  • SageMath
    [4*n-3 - ((n+1)%2) for n in range(1,71)] # G. C. Greubel, Mar 15 2024
    

Formula

From R. J. Mathar, Oct 29 2008: (Start)
G.f.: x*(1+3*x+4*x^2)/((1+x)*(1-x)^2).
a(n) = a(n-2) + 8.
a(n) + a(n+1) = A004770(n).
a(n+1) - a(n) = A010703(n). (End)
a(n) = 8*floor((n-1)/2) + 4 - 3*(n mod 2). - Reinhard Zumkeller, Dec 15 2008
a(n) = A153125(n,n). - Reinhard Zumkeller, Dec 20 2008
a(n) = 8*n - a(n-1) - 11 (with a(1)=1). - Vincenzo Librandi, Aug 06 2010
a(n) = 4*n - (7 + (-1)^n)/2. - Arkadiusz Wesolowski, Sep 18 2012
a(1)=1, a(2)=4, a(3)=9, a(n) = a(n-1) + a(n-2) - a(n-3). - Harvey P. Dale, Jun 18 2013
a(n) = 1 + A004526(n)*3 + A004526(n-1)*5. - Gregory R. Bryant, Apr 16 2014
From Franck Maminirina Ramaharo, Jul 22 2018: (Start)
a(n) = A047470(n) + 1.
E.g.f.: (8 - exp(-x) + (8*x - 7)*exp(x))/2. (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = (sqrt(2)+1)*Pi/16 + log(2)/4 + sqrt(2)*arccoth(sqrt(2))/8. - Amiram Eldar, Dec 11 2021

A171498 a(n) = 4*3^n-1.

Original entry on oeis.org

3, 11, 35, 107, 323, 971, 2915, 8747, 26243, 78731, 236195, 708587, 2125763, 6377291, 19131875, 57395627, 172186883, 516560651, 1549681955, 4649045867, 13947137603, 41841412811, 125524238435, 376572715307, 1129718145923, 3389154437771, 10167463313315, 30502389939947
Offset: 0

Views

Author

Klaus Brockhaus, Dec 10 2009

Keywords

Comments

Binomial transform of A171497.
Inverse binomial transform of A171499.

Crossrefs

Programs

  • Mathematica
    NestList[3#+2&,3,30]  (* Harvey P. Dale, Feb 25 2011 *)
  • PARI
    {m=25; v=concat([3], vector(m-1)); for(n=2, m, v[n]=3*v[n-1]+2); v}

Formula

a(n) = 3*a(n-1)+2 for n > 0; a(0) = 3.
G.f.: (3-x)/((1-x)*(1-3*x)).
a(n) = A036543(n) + 2. - Philippe Deléham, Apr 13 2013
E.g.f.: exp(x)*(4*exp(2*x) - 1). - Stefano Spezia, Aug 04 2024

Extensions

a(25)-a(27) from Stefano Spezia, Aug 04 2024

A171499 a(n) = 6*a(n-1) - 8*a(n-2) for n > 1; a(0) = 3, a(1) = 14.

Original entry on oeis.org

3, 14, 60, 248, 1008, 4064, 16320, 65408, 261888, 1048064, 4193280, 16775168, 67104768, 268427264, 1073725440, 4294934528, 17179803648, 68719345664, 274877644800, 1099511103488, 4398045462528, 17592183947264, 70368739983360
Offset: 0

Views

Author

Klaus Brockhaus, Dec 10 2009

Keywords

Comments

Binomial transform of A171498; second binomial transform of A171497; third binomial transform of A010703.
Related to sequences A001969 and A000069, sum of each group with exponent 1. - Eric Desbiaux, Jul 24 2013
a(n) in base 2 is n+2 1s followed by n 0s. - Hussam al-Homsi, Oct 12 2021

Crossrefs

Programs

  • Magma
    [4*4^n-2^n: n in [0..30]]; // Vincenzo Librandi, Jul 18 2011
    
  • Mathematica
    (* This program shows how A171499 arises from the Vandermonde determinant of (1,2,4,...,2^(n-1)). *)
    f[j_]:= 2^j - 1; z = 15;
    v[n_]:= Product[Product[f[k] - f[j], {j,k-1}], {k,2,n}]
    d[n_]:= Product[(i-1)!, {i,n}]
    Table[v[n], {n,z}]                     (* A203303 *)
    Table[v[n+1]/v[n], {n,z}]              (* A002884 *)
    Table[v[n]*v[n+2]/(2*v[n+1])^2, {n,z}]  (* A171499 *)
    (* Clark Kimberling, Jan 02 2011 *)
    LinearRecurrence[{6,-8},{3,14},30] (* Harvey P. Dale, Sep 05 2021 *)
  • PARI
    {m=23; v=concat([3, 14], vector(m-2)); for(n=3, m, v[n]=6*v[n-1]-8*v[n-2]); v}
    
  • SageMath
    [4^(n+1) -2^n for n in range(31)] # G. C. Greubel, Aug 31 2023

Formula

a(n) = 4*4^n - 2^n = 2^n * (2^(n+2) - 1).
G.f.: (3-4*x)/((1-2*x)*(1-4*x)).
a(n) = 4*a(n-1) + 2^n for n > 0. - Vincenzo Librandi, Jul 18 2011
a(n) = A171476(n+1)/2. - Hussam al-Homsi, Jun 06 2021
E.g.f.: 4*exp(4*x) - exp(2*x). - G. C. Greubel, Aug 31 2023

A171497 a(n) = 2*a(n-1) for n > 1; a(0) = 3, a(1) = 8.

Original entry on oeis.org

3, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648, 4294967296, 8589934592, 17179869184
Offset: 0

Views

Author

Klaus Brockhaus, Dec 10 2009

Keywords

Comments

8*A000079 preceded by 3.
Binomial transform of A010703.
Inverse binomial transform of A171498.

Crossrefs

Cf. A000079 (powers of 2), A010703 (repeat 3, 5), A171498.

Programs

  • Mathematica
    Join[{3},NestList[2#&,8,30]] (* Harvey P. Dale, Dec 17 2011 *)
  • PARI
    {m=30; v=concat([3, 8], vector(m-2)); for(n=3, m, v[n]=2*v[n-1]); v}

Formula

a(n) = 4*2^n for n > 0; a(0) = 3.
G.f.: (3+2*x)/(1-2*x).
E.g.f.: 4*exp(2*x) - 1. - Stefano Spezia, Aug 04 2024

Extensions

a(30)-a(32) from Stefano Spezia, Aug 04 2024

A010726 Period 2: repeat (6,10).

Original entry on oeis.org

6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10, 6, 10
Offset: 0

Views

Author

Keywords

Comments

From Klaus Brockhaus, Dec 10 2009: (Start)
Interleaving of A010722 and A010692.
Also continued fraction expansion of 3 + 4*sqrt(15)/5.
Binomial transform of 6 followed by A122803 without initial terms 1,-2.
Inverse binomial transform of A171494. (End)

Crossrefs

Equals 2*A010703. Cf. A010722 (all 6's sequence), A010692 (all 10's sequence), A122803 (powers of -2), A171494. - Klaus Brockhaus, Dec 10 2009

Programs

Formula

a(n) = -2*(-1)^n + 8. - Paolo P. Lava, Oct 27 2006
From Klaus Brockhaus, Dec 10 2009: (Start)
a(n) = a(n-2) for n > 1; a(0) = 6, a(1) = 10.
G.f.: 2*(3+5*x)/((1-x)*(1+x)). (End)

A176103 Decimal expansion of (15+sqrt(285))/10.

Original entry on oeis.org

3, 1, 8, 8, 1, 9, 4, 3, 0, 1, 6, 1, 3, 4, 1, 3, 2, 1, 8, 3, 1, 1, 6, 8, 8, 9, 4, 0, 9, 5, 2, 2, 1, 0, 9, 9, 8, 8, 8, 4, 8, 4, 7, 7, 1, 5, 7, 6, 2, 4, 8, 5, 3, 9, 5, 2, 6, 4, 9, 8, 0, 3, 7, 2, 7, 9, 3, 2, 5, 9, 6, 1, 5, 0, 2, 9, 7, 8, 0, 8, 2, 2, 6, 5, 6, 4, 2, 5, 6, 9, 7, 4, 3, 9, 0, 3, 5, 8, 8, 4, 0, 7, 3, 3, 6
Offset: 1

Views

Author

Klaus Brockhaus, Apr 10 2010

Keywords

Comments

Continued fraction expansion of (15+sqrt(285))/10 is A010703.

Examples

			(15+sqrt(285))/10 = 3.18819430161341321831...
		

Crossrefs

Cf. A176104 (decimal expansion of sqrt(285)), A010703 (repeat 3, 5).

Programs

  • Mathematica
    RealDigits[(15+Sqrt[285])/10,10,120][[1]] (* Harvey P. Dale, Aug 04 2020 *)

A176318 Decimal expansion of (15 + sqrt(285))/6.

Original entry on oeis.org

5, 3, 1, 3, 6, 5, 7, 1, 6, 9, 3, 5, 5, 6, 8, 8, 6, 9, 7, 1, 8, 6, 1, 4, 8, 2, 3, 4, 9, 2, 0, 3, 5, 1, 6, 6, 4, 8, 0, 8, 0, 7, 9, 5, 2, 6, 2, 7, 0, 8, 0, 8, 9, 9, 2, 1, 0, 8, 3, 0, 0, 6, 2, 1, 3, 2, 2, 0, 9, 9, 3, 5, 8, 3, 8, 2, 9, 6, 8, 0, 3, 7, 7, 6, 0, 7, 0, 9, 4, 9, 5, 7, 3, 1, 7, 2, 6, 4, 7, 3, 4, 5, 5, 6, 1
Offset: 1

Views

Author

Klaus Brockhaus, Apr 15 2010

Keywords

Comments

Continued fraction expansion of (15+sqrt(285))/6 is A010703 preceded by 5.

Examples

			(15+sqrt(285))/6 = 5.31365716935568869718...
		

Crossrefs

Cf. A176104 (decimal expansion of sqrt(285)), A010703 (repeat 3, 5).

Programs

  • Magma
    SetDefaultRealField(RealField(120)); (15 + Sqrt(285))/6; // G. C. Greubel, Nov 26 2019
    
  • Maple
    evalf( (15+sqrt(285))/6, 120); # G. C. Greubel, Nov 26 2019
  • Mathematica
    RealDigits[(15+Sqrt[285])/6,10,120][[1]] (* Harvey P. Dale, May 07 2017 *)
  • PARI
    default(realprecision, 120); (15+sqrt(285))/6 \\ G. C. Greubel, Nov 26 2019
    
  • Sage
    numerical_approx((15+sqrt(285))/6, digits=120) # G. C. Greubel, Nov 26 2019

A267317 a(n) = final digit of 2^n-1.

Original entry on oeis.org

0, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 13 2016

Keywords

Comments

Decimal expansion of 25/1818.
Period 4: repeat [1, 3, 7, 5] for n > 0.

Crossrefs

Programs

  • Magma
    [0] cat &cat[[1, 3, 7, 5]^^25]; // Bruno Berselli, Jan 13 2016
    
  • Maple
    A267317:=n->(2^n-1) mod 10: seq(A267317(n), n=0..150); # Wesley Ivan Hurt, Jun 15 2016
  • Mathematica
    Table[Mod[2^n - 1, 10], {n, 0, 120}]
  • PARI
    a(n) = if(n==0, 0, if(n%4==0, 5, if(n%4==1, 1, if(n%4==2, 3, if(n%4==3, 7))))) \\ Felix Fröhlich, Jan 19 2016
    
  • PARI
    a(n) = lift(Mod(2^n-1, 10)) \\ Felix Fröhlich, Jan 19 2016

Formula

G.f.: x*(1 + 2*x + 5*x^2)/(1 - x + x^2 - x^3).
a(n) = A010879(A000225(n)).
a(n) = A000689(n) - 1.
a(n) = (1+(-1)^n)*(-1)^(n*(n-1)/2)/2 + 3*(1-(-1)^n)*(-1)^(n*(n+1)/2)/2 + 4 for n > 0, a(0) = 0. [Bruno Berselli, Jan 13 2016]
From Wesley Ivan Hurt, Jun 15 2016: (Start)
a(n) = a(n-4) for n>4.
a(2k+2) = A010703(k), a(2k+1) = A010688(k). (End)
From Wesley Ivan Hurt, Jul 06 2016: (Start)
a(n) = a(n-1) - a(n-2) + a(n-3) for n > 3.
a(n) = 4 + cos(n*Pi/2) - 3*sin(n*Pi/2) for n > 0. (End)
E.g.f.: -5 + cos(x) - 3*sin(x) + 4*exp(x). - Ilya Gutkovskiy, Jul 06 2016

A306278 Numbers congruent to 2 or 11 mod 14.

Original entry on oeis.org

2, 11, 16, 25, 30, 39, 44, 53, 58, 67, 72, 81, 86, 95, 100, 109, 114, 123, 128, 137, 142, 151, 156, 165, 170, 179, 184, 193, 198, 207, 212, 221, 226, 235, 240, 249, 254, 263, 268, 277, 282, 291, 296, 305, 310, 319, 324, 333, 338, 347, 352, 361, 366, 375, 380, 389, 394
Offset: 1

Views

Author

Davis Smith, Feb 02 2019

Keywords

Crossrefs

Primes greater than 2 in this sequence: A045471.

Programs

  • Maple
    seq(seq(14*i+j, j=[2, 11]), i=0..28);
  • Mathematica
    Flatten[Table[{14n + 2, 14n + 11}, {n, 0, 28}]]
    LinearRecurrence[{1,1,-1},{2,11,16},60] (* Harvey P. Dale, Jan 16 2023 *)
  • PARI
    for(n=2, 394, if((n%14==2) || (n%14==11), print1(n, ", ")))
    
  • PARI
    for(n=1,57,print1(7*n-4+(-1)^n,", "))
    
  • PARI
    for(n=1,500,if(n%14==2,print1(n,", "));if(n%14==11,print1(n,", "))) \\ Jinyuan Wang, Feb 03 2019
    
  • PARI
    Vec(x*(2 + 9*x + 3*x^2) / ((1 - x)^2*(1 + x)) + O(x^40)) \\ Colin Barker, Mar 14 2019
    
  • PARI
    upto(n) = forstep(i = 2, n, [9, 5], print1(i", ")) \\ David A. Corneth, Mar 27 2019

Formula

a(n) = 7*n - A010703(n).
a(n) = 7*n - 4 + (-1)^n.
a(n) = a(n - 1) + a(n - 2) - a(n - 3) for n > 3.
A007310(a(n) + 1) = 7*A007310(n)
From Jinyuan Wang, Feb 03 2019: (Start)
For odd number k, a(k) = 7*k - 5.
For even number k, a(k) = 7*k - 3.
(End)
G.f.: x*(2 + 9*x + 3*x^2) / ((1 - x)^2*(1 + x)). - Colin Barker, Mar 14 2019
E.g.f.: 3 + (7*x - 4)*exp(x) + exp(-x). - David Lovler, Sep 07 2022
Showing 1-9 of 9 results.