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 1-10 of 13 results. Next

A321373 Array T(n,k) read by antidiagonals where the first row is (-1)^k*A140966(k) and each subsequent row is obtained by adding A001045(k) to the preceding one.

Original entry on oeis.org

2, 2, -1, 2, 0, 3, 2, 1, 4, 1, 2, 2, 5, 4, 7, 2, 3, 6, 7, 12, 9, 2, 4, 7, 10, 17, 20, 23, 2, 5, 8, 13, 22, 31, 44, 41, 2, 6, 9, 16, 27, 42, 65, 84, 87, 2, 7, 10, 19, 32, 53, 86, 127, 172, 169, 2, 8, 11, 22, 37, 64, 107, 170, 257, 340, 343
Offset: 0

Views

Author

Paul Curtz, Nov 08 2018

Keywords

Comments

Array:
2, -1, 3, 1, 7, 9, 23, 41, 87, ... = (-1)^n*A140966(n)
2, 0, 4, 4, 12, 20, 44, 84, 172, ... = abs(A084247(n+1))
2, 1, 5, 7, 17, 31, 65, 127, 257, ... = A014551(n)
2, 2, 6, 10, 22, 42, 86, 170, 342, ... = A078008(n+2) = A014113(n+1)
2, 3, 7, 13, 27, 53, 107, 213, 427, ... = A048573(n)
2, 4, 8, 16, 32, 64, 128, 256, 512, ... = A000079(n+1)
2, 5, 9, 19, 37, 75, 149, 299, 597, ... = A062092(n)
2, 6, 10, 22, 42, 86, 170, 342, 682, ... = A078008(n+3) = A014113(n+2).
T(n+1,k) = (-1)^k*A140966(k) + (n+1)*A001045(k).
Every row T(n+1,k) has the signature (1,2).
T(0,k) = 2, -2, 2, -2, ... = (-1)^n*2.
T(n+1,k) - T(0,k) = (n+1)*A001045(n).
5*A001045(n) is not in the OEIS.

Examples

			Triangle a(n):
  2;
  2, -1;
  2,  0,  3;
  2,  1,  4,  1;
  2,  2,  5,  4,  7;
  2,  3,  6,  7, 12,  9;
  2,  4,  7, 10, 17, 20, 23;
  etc.
Row sums: 2, 1, 5, 8, 20, 39, 83, 166, 338, 677, 1361, 2724, ... = b(n+2).
With b(0) = 2 and b(1) = 0, b(n) = b(n-1) + 2*b(n-2)  + n - 4, n > 1.
b(n) = A001045(n) - A097065(n-1).
b(n) = b(n-2) + A000225(n-2).
		

Crossrefs

Programs

  • Mathematica
    T[_, 0] = 2;
    T[0, k_] := (2^k + 5(-1)^k)/3;
    T[n_ /; n>0, k_ /; k>0] := T[n, k] = T[n-1, k] + (2^k + (-1)^(k+1))/3;
    T[, ] = 0;
    Table[T[n-k, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Nov 10 2018 *)

A048573 a(n) = a(n-1) + 2*a(n-2), a(0)=2, a(1)=3.

Original entry on oeis.org

2, 3, 7, 13, 27, 53, 107, 213, 427, 853, 1707, 3413, 6827, 13653, 27307, 54613, 109227, 218453, 436907, 873813, 1747627, 3495253, 6990507, 13981013, 27962027, 55924053, 111848107, 223696213, 447392427, 894784853, 1789569707, 3579139413, 7158278827, 14316557653
Offset: 0

Views

Author

Michael Somos, Jun 17 1999

Keywords

Comments

Number of positive integers requiring exactly n signed bits in the modified non-adjacent form representation. - Ralf Stephan, Aug 02 2003
The n-th entry (n>1) of the sequence is equal to the 1,1-entry of the n-th power of the unnormalized 4 X 4 Haar matrix: [1 1 1 0 / 1 1 -1 0 / 1 1 0 1 / 1 1 0 -1]. - Simone Severini, Oct 27 2004
Pisano period lengths: 1, 1, 6, 2, 2, 6, 6, 2, 18, 2, 10, 6, 12, 6, 6, 2, 8, 18, 18, 2, ... - R. J. Mathar, Aug 10 2012
For n >= 1, a(n) is the number of ways to tile a strip of length n+2 with blue squares and blue and red dominos, with the restriction that the first two tiles must be the same color. - Guanji Chen and Greg Dresden, Jul 15 2024

Examples

			G.f. = 2 + 3*x + 7*x^2 + 13*x^3 + 27*x^4 + 53*x^5 + 107*x^6 + 213*x^7 + 427*x^8 + ...
		

Crossrefs

Programs

  • Magma
    [(5*2^n+(-1)^n)/3: n in [0..35]]; // Vincenzo Librandi, Jul 05 2011
    
  • Mathematica
    LinearRecurrence[{1,2},{2,3},40] (* Harvey P. Dale, Dec 11 2017 *)
  • PARI
    {a(n) = if( n<0, 0, (5*2^n + (-1)^n) / 3)};
    
  • PARI
    {a(n) = if (n<0 ,0, if( n<2, n+2, a(n-1) + 2*a(n-2)))};
    
  • Sage
    [(5*2^n+(-1)^n)/3 for n in range(35)] # G. C. Greubel, Apr 10 2019

Formula

G.f.: (2 + x) / (1 - x - 2*x^2).
a(n) = (5*2^n + (-1)^n) / 3.
a(n) = 2^(n+1) - A001045(n).
a(n) = A084170(n)+1 = abs(A083581(n)-3) = A081254(n+1) - A081254(n) = A084214(n+2)/2.
a(n) = 2*A001045(n+1) + A001045(n) (note that 2 is the limit of A001045(n+1)/A001045(n)). - Paul Barry, Sep 14 2009
Let A be the Hessenberg matrix of order n, defined by: A[1,j]=1, A[i,i]:=-3, A[i,i-1]=-1, and A[i,j]=0 otherwise. Then, for n>=1, a(n-1)=-charpoly(A,-1). - Milan Janjic, Jan 27 2010
Equivalently, with different offset, a(n) = b(n+1) with b(0)=1 and b(n) = Sum_{i=0..n-1} (-1)^i (1 + (-1)^i b(i)). - Olivier Gérard, Jul 30 2012
a(n) = A000975(n-2)*10 + 5 + 2*(-1)^(n-2), a(0)=2, a(1)=3. - Yuchun Ji, Mar 18 2019
a(n+1) = Sum_{i=0..n} a(i) + 1 + (1-(-1)^n)/2, a(0)=2. - Yuchun Ji, Apr 10 2019
a(n) = 2^n + J(n+1) = J(n+2) + J(n+1) - J(n), where J is A001045. - Yuchun Ji, Apr 10 2019
a(n) = A001045(n+2) + A078008(n) = A062510(n+1) - A078008(n+1) = (A001045(n+2) + A062510(n+1))/2 = A014551(n) + 2*A001045(n). - Paul Curtz, Jul 14 2021
From Thomas Scheuerle, Jul 14 2021: (Start)
a(n) = A083322(n) + A024493(n).
a(n) = A127978(n) - A102713(n).
a(n) = A130755(n) - A166249(n).
a(n) = A007679(n) + A139763(n).
a(n) = A168642(n) XOR A007283(n).
a(n) = A290604(n) + A083944(n). (End)
From Paul Curtz, Jul 21 2021: (Start)
a(n) = 5*A001045(n) - A280560(n+1) = abs(A140360(n+1)) - A280560(n+1).
a(n) = 2^n + A001045(n+1) = A001045(n+3) - A000079(n).
a(n) = A001045(n+4) - A340627(n). (End)
a(n) = A001045(n+5) - A005010(n).
a(n+1) + a(n) = a(n+2) - a(n) = 5*2^n. - Michael Somos, Feb 22 2023
a(n) = A135318(2*n) + A135318(2*n+1) = A112387(2*n) + A112387(2*n+1). - Paul Curtz, Jun 26 2024
E.g.f.: (cosh(x) + 5*cosh(2*x) - sinh(x) + 5*sinh(2*x))/3. - Stefano Spezia, May 18 2025

Extensions

Formula of Milan Janjic moved here from wrong sequence by Paul D. Hanna, May 29 2010

A163834 a(n) = (4^n + 5)/3.

Original entry on oeis.org

2, 3, 7, 23, 87, 343, 1367, 5463, 21847, 87383, 349527, 1398103, 5592407, 22369623, 89478487, 357913943, 1431655767, 5726623063, 22906492247, 91625968983, 366503875927, 1466015503703, 5864062014807, 23456248059223, 93824992236887, 375299968947543
Offset: 0

Views

Author

Juri-Stepan Gerasimov, Aug 05 2009

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(4^n + 5)/3, {n, 0, 50}] (* G. C. Greubel, Aug 05 2017 *)
    LinearRecurrence[{5,-4},{2,3},30] (* Harvey P. Dale, Jun 14 2023 *)
  • PARI
    x='x+O('x^50); concat([0], Vec((2-7*x)/((4*x-1)*(x-1)))) \\ G. C. Greubel, Aug 05 2017

Formula

a(n) = (4^n + 5)/3 = A135351(2*n+1) = A140966(2*n) = A153643(2*n).
a(n) = 5*a(n-1) - 4*a(n-2).
G.f.: (2-7*x)/((4*x-1)*(x-1)).
a(n+1) - a(n) = A000302(n).
E.g.f.: (1/3)*(5*exp(x) + exp(4*x)). - G. C. Greubel, Aug 05 2017

Extensions

Offset set to 0 by R. J. Mathar, Aug 06 2009

A083582 a(n) = (8*2^n-5*(-1)^n)/3.

Original entry on oeis.org

1, 7, 9, 23, 41, 87, 169, 343, 681, 1367, 2729, 5463, 10921, 21847, 43689, 87383, 174761, 349527, 699049, 1398103, 2796201, 5592407, 11184809, 22369623, 44739241, 89478487, 178956969, 357913943, 715827881, 1431655767, 2863311529
Offset: 0

Views

Author

Paul Barry, May 01 2003

Keywords

Comments

Binomial transform of A083581.

Crossrefs

Cf. A140966.

Programs

Formula

a(n) = (8*2^n-5(-1)^n)/3.
G.f.: (1+6*x)/((1-2*x)*(1+x)).
E.g.f.: (8*exp(2*x)-5*exp(-x))/3.
a(n) = 6*A001045(n) + A001045(n+1). - Creighton Dement, Mar 25 2005
a(n) = 2^(n+2)th coefficient of - eta(z)^3 eta(z^5) eta(z^10)^2 /eta(z^2)^2. - Kok Seng Chua (chuaks(AT)ihpc.a-star.edu.sg), Aug 30 2005
a(n) = a(n-1)+2*a(n-2). a(n)+a(n+1) = 8*A000079 = a(n+2)-a(n). - Paul Curtz, Jul 27 2008

A154570 The main diagonal of the successive differences of A154127.

Original entry on oeis.org

1, 3, -4, 2, -6, -2, -14, -18, -46, -82, -174, -338, -686, -1362, -2734, -5458, -10926, -21842, -43694, -87378, -174766, -349522, -699054, -1398098, -2796206, -5592402, -11184814, -22369618, -44739246, -89478482, -178956974, -357913938, -715827886
Offset: 0

Views

Author

Paul Curtz, Jan 12 2009

Keywords

Crossrefs

Programs

Formula

a(n) = a(n-1) + 2*a(n-2), n>0.
a(n+2) = 2*(-1)^(n+1)*A140966(n).
a(n+5) = -2*A083582(n).
a(2n+1) = 3 - A078008(2n) = 3 - A047849(n).
a(2n+2) = -4 - A078008(2n+1) = -4 - A020988(n).
G.f.: (1+2*x-9*x^2)/((1+x)*(1-2*x)). - R. J. Mathar, Feb 25 2009

Extensions

Edited and extended by R. J. Mathar, Feb 25 2009

A171160 a(n) = a(n-1) + 2*a(n-2) with a(0)=3, a(1)=4.

Original entry on oeis.org

3, 4, 10, 18, 38, 74, 150, 298, 598, 1194, 2390, 4778, 9558, 19114, 38230, 76458, 152918, 305834, 611670, 1223338, 2446678, 4893354, 9786710, 19573418, 39146838, 78293674, 156587350, 313174698, 626349398, 1252698794, 2505397590, 5010795178, 10021590358
Offset: 0

Views

Author

Paul Curtz, Dec 04 2009

Keywords

Crossrefs

Programs

Formula

a(n) = (1/3)*(2*(-1)^n + 7*2^n), with n>=0. - Paolo P. Lava, Dec 14 2009
G.f.: -(x+3) / ((x+1)*(2*x-1)). - Colin Barker, Feb 10 2015
From Paul Curtz, Jun 03 2022: (Start)
a(n) = A078008(n) + A078008(n+1) + A078008(n+2).
a(n) = 2^(n+1) + A078008(n).
a(n) = A001045(n+3) - A001045(n).
(a(n) + a(n+1) = a(n+2) - a(n) = A005009(n).)
a(n) + a(n+3) = A175805(n).
a(n) = A062510(n) + A083582(n-1) with A083582(-1) = 3.
a(n) = A092297(n) + A154879(n). (End)
a(n) = 2*A062092(n-1), for n>0; 2*a(n) = A083595(n+1). - Paul Curtz, Jun 08 2022

Extensions

Edited by N. J. A. Sloane, Dec 05 2009
More terms from J. Mulder (jasper.mulder(AT)planet.nl), Jan 28 2010
More terms from Max Alekseyev, Apr 24 2010

A156550 a(n) = 5*(-1)^n*A078008(n).

Original entry on oeis.org

5, 0, 10, -10, 30, -50, 110, -210, 430, -850, 1710, -3410, 6830, -13650, 27310, -54610, 109230, -218450, 436910, -873810, 1747630, -3495250, 6990510, -13981010, 27962030, -55924050, 111848110, -223696210, 447392430, -894784850, 1789569710, -3579139410
Offset: 0

Views

Author

Paul Curtz, Feb 09 2009

Keywords

Crossrefs

Programs

Formula

a(n) = A140966(n)+A140966(n+2).
a(n) = 3*A140966(n)-A140966(n+1).
a(n+1) = 10*(-1)^n*A001045(n).
G.f.: 5*(1+x)/(1+x-2*x^2). - R. J. Mathar, Feb 23 2009
a(n) = (5*(2+(-2)^n))/3. - Colin Barker, Jun 10 2012
a(n) = -a(n-1) + 2*a(n-2) for n > 1. - Klaus Purath, Jan 30 2021
E.g.f.: 5*exp(-2*x)*(1 + 2*exp(3*x))/3. - Stefano Spezia, Jan 30 2021

Extensions

Edited and extended by R. J. Mathar Feb 23 2009

A171501 Inverse binomial transform of A084640.

Original entry on oeis.org

0, 1, 3, -1, 7, -9, 23, -41, 87, -169, 343, -681, 1367, -2729, 5463, -10921, 21847, -43689, 87383, -174761, 349527, -699049, 1398103, -2796201, 5592407, -11184809, 22369623, -44739241, 89478487, -178956969, 357913943, -715827881
Offset: 0

Views

Author

Paul Curtz, Dec 10 2009

Keywords

Comments

a(n) and differences are
0, 1, 3, -1, 7, -9,
1, 2, -4, 8, -16, 32, =(-1)^(n+1) * A171449(n),
1, -6, 12, -24, 48, -96,
-7, 18, -36, 72, -144, 288,
25, -54, 108, -216, 432, -864,
Vertical: 1) 0 followed with A168589(n).
2) (-1 followed with A008776(n) ) signed. See A025192(n).
Main diagonal: see A167747(1+n). - Paul Curtz, Jun 16 2011

Programs

  • Magma
    I:=[0, 1, 3]; [n le 3 select I[n] else -Self(n-1) + 2*Self(n-2): n in [1..40]]; // Vincenzo Librandi, Oct 18 2012
  • Mathematica
    CoefficientList[Series[x*(1 + 4*x)/((1 + 2*x)*(1 - x)), {x, 0, 30}], x]
    LinearRecurrence[{-1,2},{0,1,3},40] (* Harvey P. Dale, Jan 14 2020 *)

Formula

a(n) = A140966(n), n>0.
G.f.: x*(1+4*x) / ( (1+2*x)*(1-x) ). - R. J. Mathar, Jun 14 2011
a(1+n)= (-1)^(1+n) * A001045(1+n) + 2. - Paul Curtz, Jun 16 2011

Extensions

Mathematica program by Olivier Gérard, Jul 06 2011

A247525 a(n) = 5 * a(n-1) - 2 * a(n-1)^2 / a(n-2), with a(0) = 1, a(1) = 2.

Original entry on oeis.org

1, 2, 2, 6, -6, -42, 378, 8694, -356454, -31011498, 5240943162, 1797643504566, -1224195226609446, -1673474874775112682, 4566912933261282509178, 24949045354406386347639414, -272468524315472145302570040294, -5952619850720119958425247670303018
Offset: 0

Views

Author

Michael Somos, Sep 18 2014

Keywords

Crossrefs

Cf. A140966.

Programs

  • Magma
    I:=[1, 2]; [n le 2 select I[n] else 5*Self(n-1) - 2*Self(n-1)^2/Self(n-2): n in [1..30]]; // G. C. Greubel, Aug 05 2018
  • Mathematica
    RecurrenceTable[{a[n] == 5*a[n - 1] - 2*a[n - 1]^2/a[n - 2], a[0] == 1, a[1] == 2}, a, {n, 0, 50}] (* G. C. Greubel, Aug 05 2018 *)
  • PARI
    {a(n) = if( n<0, 1 / prod(k=1, -n, (5 + (-2)^-k) / 3), prod(k=0, n-1, (5 + (-2)^k) / 3))};
    

Formula

0 = a(n)*(-5*a(n+1) + a(n+2)) + a(n+1)*(+2*a(n+1)) for all n in Z.
a(n+1) = a(n) * A140966(n) for all n in Z.

A268741 a(n) = 2*a(n - 2) - a(n - 1) for n>1, a(0) = 4, a(1) = 5.

Original entry on oeis.org

4, 5, 3, 7, -1, 15, -17, 47, -81, 175, -337, 687, -1361, 2735, -5457, 10927, -21841, 43695, -87377, 174767, -349521, 699055, -1398097, 2796207, -5592401, 11184815, -22369617, 44739247, -89478481, 178956975, -357913937, 715827887, -1431655761, 2863311535
Offset: 0

Views

Author

Ilya Gutkovskiy, Feb 12 2016

Keywords

Comments

In general, the ordinary generating function for the recurrence relation b(n) = 2*b(n - 2) - b(n - 1) with n>1 and b(0)=k, b(1)=m, is (k + (k + m)*x)/(1 + x - 2*x^2). This recurrence gives the closed form a(n) = ((-2)^n*(k - m) + 2*k + m).

Examples

			a(0) = (5 + 3)/2 = 4  because a(1) = 5, a(2) = 3;
a(1) = (3 + 7)/2 = 5  because a(2) = 3, a(3) = 7;
a(2) = (7 - 1)/2 = 3  because a(3) = 7, a(4) = -1, etc.
		

Crossrefs

Programs

  • Magma
    [(13-(-2)^n)/3: n in [0..35]]; // Vincenzo Librandi, Feb 13 2016
    
  • Mathematica
    Table[(13 - (-2)^n)/3, {n, 0, 33}]
    LinearRecurrence[{-1, 2}, {4, 5}, 34]
    RecurrenceTable[{a[1] == 4, a[2] == 5, a[n] == 2*a[n-2] - a[n-1]}, a, {n, 50}] (* Vincenzo Librandi, Feb 13 2016 *)
  • PARI
    Vec((4 + 9*x)/(1 + x - 2*x^2) + O(x^40)) \\ Michel Marcus, Feb 25 2016

Formula

G.f.: (4 + 9*x)/(1 + x - 2*x^2).
a(n) = (13 - (-2)^n)/3.
a(n) = A084247(n) + 3.
a(n) = (-1)^n*A154570(n+1) + 1.
a(n) = (-1)^(n-1)*A171382(n-1) + 2.
Limit_{n -> oo} a(n)/a(n + 1) = -1/2.
a(n) = 4 - (-1)^n *A001045(n). - Paul Curtz, Feb 26 2024
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