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 1-4 of 4 results.

A110594 a(1) = 4, a(2) = 12, for n>1: a(n) = 3*4^(n-1).

Original entry on oeis.org

4, 12, 48, 192, 768, 3072, 12288, 49152, 196608, 786432, 3145728, 12582912, 50331648, 201326592, 805306368, 3221225472, 12884901888, 51539607552, 206158430208, 824633720832, 3298534883328, 13194139533312, 52776558133248
Offset: 1

Views

Author

Jonathan Vos Post, Jul 29 2005

Keywords

Crossrefs

Programs

  • GAP
    Concatenation([4],List([2..25],n->3*4^(n-1))); # Muniru A Asiru, Oct 21 2018
  • Magma
    [4] cat [3*4^(n-1): n in [2..30]]; // Vincenzo Librandi, May 29 2014
    
  • Maple
    seq(coeff(series(4*x*(1-x)/(1-4*x),x,n+1), x, n), n = 1 .. 25); # Muniru A Asiru, Oct 21 2018
  • Mathematica
    CoefficientList[Series[4 (1 - x)/(1 - 4 x), {x, 0, 40}], x] (* Vincenzo Librandi, May 29 2014 *)
  • PARI
    x='x+O('x^50); Vec(4*x*(1 - x)/(1 - 4*x)) \\ G. C. Greubel, Sep 01 2017
    

Formula

a(n) = A002001(n), n>1. - R. J. Mathar, Aug 18 2008
G.f.: 4*x*(1 - x)/(1 - 4*x). - Vincenzo Librandi, May 29 2014

Extensions

Definition corrected by R. J. Mathar, Aug 18 2008

A103457 a(n) = 3^n + 1 - 0^n.

Original entry on oeis.org

1, 4, 10, 28, 82, 244, 730, 2188, 6562, 19684, 59050, 177148, 531442, 1594324, 4782970, 14348908, 43046722, 129140164, 387420490, 1162261468, 3486784402, 10460353204, 31381059610, 94143178828, 282429536482, 847288609444
Offset: 0

Views

Author

Paul Barry, Feb 07 2005

Keywords

Crossrefs

Programs

  • Magma
    [1] cat [3^n + 1: n in [1..30]]; // G. C. Greubel, Jun 22 2021
    
  • Mathematica
    Join[{1},LinearRecurrence[{4,-3},{4,10},30]] (* Harvey P. Dale, Mar 29 2015 *)
  • PARI
    my(x='x+O('x^50)); Vec((1-3*x^2)/((1-x)*(1-3*x))) \\ Altug Alkan, Dec 04 2015
    
  • Sage
    [1]+[3^n + 1 for n in (1..30)] # G. C. Greubel, Jun 22 2021

Formula

G.f.: (1-3*x^2)/((1-x)*(1-3*x)).
a(n) = Sum_{k=0..n} binomial(n, k)*0^(k(n-k))*3^k.
From R. J. Mathar, Aug 04 2008: (Start)
a(n) = A034472(n), n>0.
a(n) = A094388(n-1), n>1.
a(n+1) - a(n) = A110593(n+1). (End)
a(n) = 3*a(n-1) - 2, with a(1)=4. - Vincenzo Librandi, Dec 29 2010
From J. Conrad, Nov 25 2015: (Start)
For n>0, a(n) = 2 * (A011782(0) + A011782(n) + Sum_{x=1..n-1} Sum_{k=0..x-1}(binomial(x-1,k)*(A011782(k+1) + A011782(n-x+k)))).
Alternatively, for n>0, a(n) = A027649(n) - 2 * Sum_{x=1..n-1}Sum_{k=0..x-1}(binomial(x-1,k)*(A011782(k+1) + A011782(n-x+k))). (End)
E.g.f.: -1 + exp(x) + exp(3*x). - G. C. Greubel, Jun 22 2021

A164907 a(n) = (3*3^n-(-1)^n)/2.

Original entry on oeis.org

1, 5, 13, 41, 121, 365, 1093, 3281, 9841, 29525, 88573, 265721, 797161, 2391485, 7174453, 21523361, 64570081, 193710245, 581130733, 1743392201, 5230176601, 15690529805, 47071589413, 141214768241, 423644304721, 1270932914165
Offset: 0

Views

Author

Klaus Brockhaus, Aug 31 2009

Keywords

Comments

Interleaving of A096053 and A083884 without initial term 1.
Partial sums are (essentially) in A080926.
First differences are (essentially) in A105723.
a(n)+a(n+1) = A008776(n+1) = A099856(n+1) = A110593(n+2).
Binomial transform of A056450. Inverse binomial transform of A164908.

Crossrefs

Equals A046717 without initial term 1 and A080925 without initial term 0. Equals A084182 / 2 from second term onward.

Programs

Formula

a(n) = 2*a(n-1)+3*a(n-2) for n > 1; a(0) = 1, a(1) = 5.
G.f.: (1+3*x)/((1+x)*(1-3*x)).
a(n) = 3*a(n-1)+2*(-1)^n. - Carmine Suriano, Mar 21 2014

A110595 a(1)=5. For n > 1, a(n) = 4*5^(n-1) = A005054(n).

Original entry on oeis.org

5, 20, 100, 500, 2500, 12500, 62500, 312500, 1562500, 7812500, 39062500, 195312500, 976562500, 4882812500, 24414062500, 122070312500, 610351562500, 3051757812500, 15258789062500, 76293945312500, 381469726562500
Offset: 1

Views

Author

Jonathan Vos Post, Jul 29 2005

Keywords

Comments

a(n) is the number of n-digit integers that contain only even digits (A014263). - Bernard Schott, Nov 11 2022

Crossrefs

Programs

  • Mathematica
    Join[{5},NestList[5#&,20,20]] (* Harvey P. Dale, Jun 19 2013 *)
    Rest[CoefficientList[Series[5 x (1 - x)/(1 - 5 x), {x,0,50}], x]] (* G. C. Greubel, Sep 01 2017 *)
  • PARI
    my(x='x+O('x^50)); Vec(5*x*(1-x)/(1-5*x)) \\ G. C. Greubel, Sep 01 2017

Formula

O.g.f.: 5*x*(1-x)/(1-5*x). - Better definition from R. J. Mathar, May 13 2008
Sum_{n>=1} 1/a(n) = 21/80. - Bernard Schott, Nov 11 2022

Extensions

Better definition from R. J. Mathar, May 13 2008
Incorrect comment removed by Michel Marcus, Nov 11 2022
Showing 1-4 of 4 results.