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.

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A171418 Expansion of (1+x)^4/(1-x).

Original entry on oeis.org

1, 5, 11, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16
Offset: 0

Views

Author

Richard Choulet, Dec 08 2009

Keywords

Comments

For n>=4 a(n)=2^4=16. This sequence is the transform of A115291 by the following transform T: T(u_0,u_1,u_2,u_3,u_4,...)=(u_0, u_0+u_1, u_1+u_2,u_2+u_3, ...); we observe that T(A040000)=A113311 and also T(A113311)=A115291.
Also continued fraction expansion of (55305+sqrt(65))/46231. - Bruno Berselli, Sep 23 2011

Examples

			a(3) = C(5,3-0)+C(5,3-2) = 10+5 = 15.
		

Crossrefs

Programs

  • Maple
    m:=5:for n from 0 to m+1 do a(n):=sum('binomial(m,n-2*k)',k=0..floor(n/2)): od : seq(a(n),n=0..m+1);

Formula

a(n) = Sum_{k=0..floor(n/2)} binomial(5,n-2*k).

Extensions

Definition rewritten by Bruno Berselli, Sep 23 2011

A255740 Square array read by antidiagonals upwards: T(n,1) = 1; for k > 1, T(n,k) = (n-1)*(n-2)^(A000120(k-1)-1) with n >= 1.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 2, 0, 0, 1, 4, 3, 2, 1, 0, 1, 5, 4, 6, 2, 0, 0, 1, 6, 5, 12, 3, 2, 0, 0, 1, 7, 6, 20, 4, 6, 2, 0, 0, 1, 8, 7, 30, 5, 12, 6, 2, 1, 0, 1, 9, 8, 42, 6, 20, 12, 12, 2, 0, 0, 1, 10, 9, 56, 7, 30, 20, 36, 3, 2, 0, 0, 1, 11, 10, 72, 8, 42, 30, 80, 4, 6, 2, 0, 0, 1, 12, 11, 90, 9, 56, 42, 150, 5, 12, 6, 2, 0, 0
Offset: 1

Views

Author

Omar E. Pol, Mar 05 2015

Keywords

Comments

The partial sums of row n give the n-th row of the square array A255741.

Examples

			The corner of the square array with the first 16 terms of the first 12 rows looks like this:
-------------------------------------------------------------------------
A000007: 1, 0, 0,  0, 0,  0,  0,   0, 0,  0,  0,   0,  0,   0,   0,    0
A255738: 1, 1, 1,  0, 1,  0,  0,   0  1,  0,  0,   0,  0,   0,   0,    0
A040000: 1, 2, 2,  2, 2,  2,  2,   2, 2,  2,  2,   2,  2,   2,   2,    2
A151787: 1, 3, 3,  6, 3,  6,  6,  12, 3,  6,  6,  12,  6,  12,  12,   24
A147582: 1, 4, 4, 12, 4, 12, 12,  36, 4, 12, 12,  36, 12,  36,  36,  108
A151789: 1, 5, 5, 20, 5, 20, 20,  80, 5, 20, 20,  80, 20,  80,  80,  320
A151779: 1, 6, 6, 30, 6, 30, 30, 150, 6, 30, 30, 150, 30, 150, 150,  750
A151791: 1, 7, 7, 42, 7, 42, 42, 252, 7, 42, 42, 252, 42, 252, 252, 1512
A151782: 1, 8, 8, 56, 8, 56, 56, 392, 8, 56, 56, 392, 56, 392, 392, 2744
A255743: 1, 9, 9, 72, 9, 72, 72, 576, 9, 72, 72, 576, 72, 576, 576, 4608
A255744: 1,10,10, 90,10, 90, 90, 810,10, 90, 90, 810, 90, 810, 810, 7290
A255745: 1,11,11,110,11,110,110,1100,11,110,110,1100,110,1100,1100,11000
...
		

Crossrefs

Column 1 is A000012.
Columns 2^k+1, for k >=0: A011477.
Columns 4, 6, 7, 10, 11, 13...: 0 together with A002378.

Programs

  • PARI
    tabl(nn) = {for (n=1, nn, for (k=1, nn, if (k==1, x = 1, x= (n-1)*(n-2)^(hammingweight(k-1)-1)); print1(x, ", ");); print(););} \\ Michel Marcus, Mar 15 2015

Formula

T(n,1) = 1; for k > 1, T(n,k) = (n-1)*(n-2)^(A000120(k-1)-1) with n >= 1.

A054458 Convolution triangle based on A001333(n), n >= 1.

Original entry on oeis.org

1, 3, 1, 7, 6, 1, 17, 23, 9, 1, 41, 76, 48, 12, 1, 99, 233, 204, 82, 15, 1, 239, 682, 765, 428, 125, 18, 1, 577, 1935, 2649, 1907, 775, 177, 21, 1, 1393, 5368, 8680, 7656, 4010, 1272, 238, 24, 1, 3363, 14641, 27312, 28548, 18358, 7506, 1946, 308, 27, 1
Offset: 0

Views

Author

Wolfdieter Lang, Apr 26 2000

Keywords

Comments

In the language of the Shapiro et al. reference (given in A053121) such a lower triangular (ordinary) convolution array, considered as a matrix, belongs to the Bell-subgroup of the Riordan-group.
The G.f. for the row polynomials p(n,x) (increasing powers of x) is LPell(z)/(1-x*z*LPell(z)) with LPell(z) given in 'Formula'.
Column sequences are A001333(n+1), A054459(n), A054460(n) for m=0..2.
Mirror image of triangle in A209696. - Philippe Deléham, Mar 24 2012
Subtriangle of the triangle given by (0, 3, -2/3, -1/3, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938. - Philippe Deléham, Mar 25 2012
Riordan array ((1+x)/(1-2*x-x^2), (x+x^2)/(1-2*x-x^2)). - Philippe Deléham, Mar 25 2012

Examples

			Fourth row polynomial (n=3): p(3,x)= 17+23*x+9*x^2+x^3.
Triangle begins :
  1
  3, 1
  7, 6, 1
  17, 23, 9, 1
  41, 76, 48, 12, 1
  99, 233, 204, 82, 15, 1
  239, 682, 765, 428, 125, 18, 1. - _Philippe Deléham_, Mar 25 2012
(0, 3, -2/3, -1/3, 0, 0, 0, ...) DELTA (1, 0, 0, 0, ...) begins :
  1
  0, 1
  0, 3, 1
  0, 7, 6, 1
  0, 17, 23, 9, 1
  0, 41, 76, 48, 12, 1
  0, 99, 233, 204, 82, 15, 1
  0, 239, 682, 765, 428, 125, 15, 1. - _Philippe Deléham_, Mar 25 2012
		

Crossrefs

Cf. A002203(n+1)/2. Row sums: A055099(n).

Formula

a(n, m) := ((n-m+1)*a(n, m-1) + (2n-m)*a(n-1, m-1) + (n-1)*a(n-2, m-1))/(4*m), n >= m >= 1; a(n, 0)= A001333(n+1); a(n, m) := 0 if n
G.f. for column m: LPell(x)*(x*LPell(x))^m, m >= 0, with LPell(x)= (1+x)/(1-2*x-x^2) = g.f. for A001333(n+1).
G.f.: (1+x)/(1-2*x-y*x-x^2-y*x^2). - Philippe Deléham, Mar 25 2012
T(n,k) = 2*T(n-1,k) + T(n-1,k-1) + T(n-2,k) + T(n-2,k-1), T(0,0) = T(1,1) = 1, T(1,0) = 3 and T(n,k) = 0 if k<0 or if k>n. - Philippe Deléham, Mar 25 2012
Sum_{k=0..n} T(n,k)*x^k = A040000(n), A001333(n+1), A055099(n), A126473(n), A126501(n), A126528(n) for x = -1, 0, 1, 2, 3, 4 respectively. - Philippe Deléham, Mar 25 2012

A097808 Riordan array ((1+2x)/(1+x)^2, 1/(1+x)) read by rows.

Original entry on oeis.org

1, 0, 1, -1, -1, 1, 2, 0, -2, 1, -3, 2, 2, -3, 1, 4, -5, 0, 5, -4, 1, -5, 9, -5, -5, 9, -5, 1, 6, -14, 14, 0, -14, 14, -6, 1, -7, 20, -28, 14, 14, -28, 20, -7, 1, 8, -27, 48, -42, 0, 42, -48, 27, -8, 1, -9, 35, -75, 90, -42, -42, 90, -75, 35, -9, 1, 10, -44, 110, -165, 132, 0, -132, 165, -110, 44, -10, 1
Offset: 0

Author

Paul Barry, Aug 25 2004

Keywords

Comments

Inverse of A059260. Row sums are inverse binomial transform of A040000, with g.f. (1+2x)/(1+x). Diagonal sums are (-1)^n(1-Fib(n)). A097808=B^(-1)*A097806, where B is the binomial matrix. B*A097808*B^(-1) is the inverse of A097805.

Examples

			Rows begin
1;
0, 1;
-1, -1, 1;
2, 0, -2, 1;
-3, 2, 2, -3, 1;
4, -5, 0, 5, -4, 1;
-5, 9, -5, -5, 9, -5, 1;
6, -14, 14, 0, -14, 14, -6, 1;
-7, 20, -28, 14, 14, -28, 20, -7, 1;
8, -27, 48, -42, 0, 42, -48, 27, -8, 1;
		

Programs

  • Maple
    T:= proc(n,k) option remember;
    if k < 0 or k > n then return 0 fi;
    procname (n-1,k-1)-3*procname(n-1,k)+2*procname(n-2,k-1)-3*procname(n-2,k)+
    procname(n-3,k-1)-procname(n-3,k)
    end proc:
    T(0,0):= 1: T(1,1):= 1: T(2,2):= 1:
    T(1,0):= 0: T(2,0):= -1: T(2,1):= -1:
    seq(seq(T(n,k),k=0..n),n=0..12); # Robert Israel, Jul 16 2019
  • Mathematica
    (* The function RiordanArray is defined in A256893. *)
    RiordanArray[(1 + 2 #)/(1 + #)^2&, #/(1 + #)&, 12] // Flatten (* Jean-François Alcover, Jul 16 2019 *)

Formula

Columns have g.f. (1+2x)/(1+x)^2(x/(1+x))^k.
T(n,k)=T(n-1,k-1)-3*T(n-1,k)+2*T(n-2,k-1)-3*T(n-2,k)+T(n-3,k-1)-T(n-3,k), T(0,0)=T(1,1)=T(2,2)=1, T(1,0)=0, T(2,0)=T(2,1)=-1, T(n,k)=0 if k<0 or if k>n. - Philippe Deléham, Jan 12 2014
T(0,0)=1, T(n,0)=(-1)^(n-1)*(n-1) for n>0, T(n,n)=1, T(n,k)=T(n-1,k-1)-T(n-1,k) for 0Philippe Deléham, Jan 12 2014

A101104 a(1)=1, a(2)=12, a(3)=23, and a(n)=24 for n>=4.

Original entry on oeis.org

1, 12, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24
Offset: 1

Author

Cecilia Rossiter, Dec 15 2004

Keywords

Comments

Original name: The first summation of row 4 of Euler's triangle - a row that will recursively accumulate to the power of 4.

Crossrefs

For other sequences based upon MagicNKZ(n,k,z):
..... | n = 1 | n = 2 | n = 3 | n = 4 | n = 5 | n = 6 | n = 7
---------------------------------------------------------------------------
z = 0 | A000007 | A019590 | .......MagicNKZ(n,k,0) = A008292(n,k+1) .......
z = 1 | A000012 | A040000 | A101101 | thisSeq | A101100 | ....... | .......
z = 2 | A000027 | A005408 | A008458 | A101103 | A101095 | ....... | .......
z = 3 | A000217 | A000290 | A003215 | A005914 | A101096 | ....... | .......
z = 4 | A000292 | A000330 | A000578 | A005917 | A101098 | ....... | .......
z = 5 | A000332 | A002415 | A000537 | A000583 | A022521 | ....... | A255181
Cf. A101095 for an expanded table and more about MagicNKZ.

Programs

  • Mathematica
    MagicNKZ = Sum[(-1)^j*Binomial[n+1-z, j]*(k-j+1)^n, {j, 0, k+1}];Table[MagicNKZ, {n, 4, 4}, {z, 1, 1}, {k, 0, 34}]
    Join[{1, 12, 23},LinearRecurrence[{1},{24},56]] (* Ray Chandler, Sep 23 2015 *)

Formula

a(k) = MagicNKZ(4,k,1) where MagicNKZ(n,k,z) = Sum_{j=0..k+1} (-1)^j*binomial(n+1-z,j)*(k-j+1)^n (cf. A101095). That is, a(k) = Sum_{j=0..k+1} (-1)^j*binomial(4, j)*(k-j+1)^4.
a(1)=1, a(2)=12, a(3)=23, and a(n)=24 for n>=4. - Joerg Arndt, Nov 30 2014
G.f.: x*(1+11*x+11*x^2+x^3)/(1-x). - Colin Barker, Apr 16 2012

Extensions

New name from Joerg Arndt, Nov 30 2014
Original Formula edited and Crossrefs table added by Danny Rorabaugh, Apr 22 2015

A165326 a(0)=a(1)=1, a(n) = -a(n-1) for n > 1.

Original entry on oeis.org

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

Author

Philippe Deléham, Sep 14 2009

Keywords

Comments

Inverse binomial transform of A040000(n) = 1,2,2,2,2,...; binomial transform of (-1)^(n+1)*A000918(n) = 1,0,-2,6,-14,30,-62,... - Philippe Deléham, Sep 16 2009
This is also the Z-sequence of the Riordan triangle A105809. See the W. Lang link under A006232 for Riordan A- and Z-sequences. - Wolfdieter Lang, Oct 04 2014

Crossrefs

Cf. A033999.

Programs

  • Mathematica
    PadRight[{1},120,{-1,1}] (* Harvey P. Dale, Dec 04 2012 *)
    Join[{1},LinearRecurrence[{-1},{1},83]] (* Ray Chandler, Aug 12 2015 *)

Formula

G.f.: (1+2*x)/(1+x).
E.g.f.: 2-exp(-x).
a(n) = -a(n-1). - Wesley Ivan Hurt, Apr 23 2021

A171440 Expansion of (1+x)^5/(1-x).

Original entry on oeis.org

1, 6, 16, 26, 31, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32
Offset: 0

Author

Richard Choulet, Dec 09 2009

Keywords

Comments

a(n)=2^5=32 for n>=5. We observe that this sequence is the transform of A171418 by T such that: T(u_0,u_1,u_2,u_3,u_4,u_5,...)=(u_0,u_0+u_1,u_1+u_2,u_2+u_3,u_3+u_4,...).
Also continued fraction expansion of (229657824-sqrt(257))/197139199. - Bruno Berselli, Sep 23 2011

Examples

			a(4) = C(6,4-0)+C(6,4-2)+C(6,4-4) = 15+15+1 = 31.
		

Programs

  • Mathematica
    PadRight[{1,6,16,26,31},100,32] (* Harvey P. Dale, Oct 01 2013 *)

Formula

With m=6, a(n) = Sum_{k=0..floor(n/2)} binomial(m,n-2*k).

Extensions

Definition rewritten by Bruno Berselli, Sep 23 2011

A171443 Expansion of g.f. (1+x)^8/(1-x).

Original entry on oeis.org

1, 9, 37, 93, 163, 219, 247, 255, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256
Offset: 0

Author

Richard Choulet, Dec 09 2009

Keywords

Comments

a(n)=2^8=256 for n>=8. We observe that this sequence is the transform of A171442 by T such that: T(u_0,u_1,u_2,u_3,u_4,u_5,...)=(u_0,u_0+u_1,u_1+u_2,u_2+u_3,u_3+u_4,...).

Examples

			a(7) = C(9,7-0)+C(9,7-2)+C(9,7-4)+C(9,7-6) = 36+126+84+9 = 255.
		

Programs

  • Maple
    m:=9:for n from 0 to 40 do a(n):=sum('binomial(m,n-2*k)',k=0..floor(n/2)): od : seq(a(n),n=0..40);
  • Mathematica
    CoefficientList[Series[(1+x)^8/(1-x),{x,0,80}],x] (* Harvey P. Dale, Jul 22 2014 *)

Formula

With m=9, a(n) = Sum_{k=0..floor(n/2)} binomial(m,n-2*k).

Extensions

Definition rewritten by Bruno Berselli, Sep 23 2011

A277561 a(n) = Sum_{k=0..n} ({binomial(n+2k,2k)*binomial(n,k)} mod 2).

Original entry on oeis.org

1, 2, 2, 2, 2, 4, 2, 2, 2, 4, 4, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 8, 4, 4, 2, 4, 4, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 8, 4, 4, 4, 8, 8, 8, 4, 8, 4, 4, 2, 4, 4, 4, 4, 8, 4, 4, 2, 4, 4, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 8, 4, 4, 4, 8, 8, 8, 4, 8, 4, 4, 4, 8, 8, 8, 8, 16, 8
Offset: 0

Author

Chai Wah Wu, Oct 19 2016

Keywords

Comments

Equals the run length transform of A040000: 1,2,2,2,2,2,...

Crossrefs

Programs

  • Magma
    A277561:= func< n | (&+[(Binomial(n+2*k, 2*k)*Binomial(n,k)) mod 2 : k in [0..n]]) >;
    [A277561(n): n in [0..100]]; // G. C. Greubel, Sep 06 2025
  • Mathematica
    Table[Sum[Mod[Binomial[n + 2 k, 2 k] Binomial[n, k], 2], {k, 0, n}], {n, 0, 86}] (* Michael De Vlieger, Oct 21 2016 *)
  • PARI
    a(n) = sum(k=0, n, binomial(n+2*k, 2*k)*binomial(n,k) % 2); \\ Michel Marcus, Oct 21 2016
    
  • Python
    def A277561(n):
        return sum(int(not (~(n+2*k) & 2*k) | (~n & k)) for k in range(n+1))
    

Formula

a(n) = 2^A069010(n). a(2n) = a(n), a(4n+1) = 2a(n), a(4n+3) = a(2n+1). - Chai Wah Wu, Nov 04 2016
a(n) = A034444(A005940(1+n)). - Antti Karttunen, May 29 2017

A302996 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals: A(n,k) = [x^(n^2)] theta_3(x)^k, where theta_3() is the Jacobi theta function.

Original entry on oeis.org

1, 1, 0, 1, 2, 0, 1, 4, 2, 0, 1, 6, 4, 2, 0, 1, 8, 6, 4, 2, 0, 1, 10, 24, 30, 4, 2, 0, 1, 12, 90, 104, 6, 12, 2, 0, 1, 14, 252, 250, 24, 30, 4, 2, 0, 1, 16, 574, 876, 730, 248, 30, 4, 2, 0, 1, 18, 1136, 3542, 4092, 1210, 312, 54, 4, 2, 0, 1, 20, 2034, 12112, 18494, 7812, 2250, 456, 6, 4, 2, 0
Offset: 0

Author

Ilya Gutkovskiy, Apr 17 2018

Keywords

Comments

A(n,k) is the number of ordered ways of writing n^2 as a sum of k squares.

Examples

			Square array begins:
  1,  1,   1,   1,    1,     1,  ...
  0,  2,   4,   6,    8,    10,  ...
  0,  2,   4,   6,   24,    90,  ...
  0,  2,   4,  30,  104,   250,  ...
  0,  2,   4,   6,   24,   730,  ...
  0,  2,  12,  30,  248,  1210,  ...
		

Crossrefs

Columns k=0..4,7 give A000007, A040000, A046109, A016725, A267326, A361695.
Main diagonal gives A232173.

Programs

  • Maple
    b:= proc(n, t) option remember; `if`(n=0, 1, `if`(n<0 or t<1, 0,
          b(n, t-1)+2*add(b(n-j^2, t-1), j=1..isqrt(n))))
        end:
    A:= (n, k)-> b(n^2, k):
    seq(seq(A(n,d-n), n=0..d), d=0..12);  # Alois P. Heinz, Mar 10 2023
  • Mathematica
    Table[Function[k, SeriesCoefficient[EllipticTheta[3, 0, x]^k, {x, 0, n^2}]][j - n], {j, 0, 11}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[Sum[x^i^2, {i, -n, n}]^k, {x, 0, n^2}]][j - n], {j, 0, 11}, {n, 0, j}] // Flatten

Formula

A(n,k) = [x^(n^2)] (Sum_{j=-infinity..infinity} x^(j^2))^k.
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