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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A130713 a(0)=a(2)=1, a(1)=2, a(n)=0 for n > 2.

Original entry on oeis.org

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

Views

Author

Paul Curtz and Tanya Khovanova, Jul 01 2007

Keywords

Comments

Self-convolution of A019590. Up to a sign the convolutional inverse of the natural numbers sequence. - Tanya Khovanova, Jul 14 2007
Iterated partial sums give the chain A130713 -> A113311 -> A008574 -> A001844 -> A005900 -> A006325 -> A033455 -> A259181, up to index. The k-th term of the n-th partial sums is (n^2-7n+14 + 4k(k+n-4))(k+n-4)!/(k-1)!/(n-1)!, for k > 3-n. Iterating partial sums in reverse (n-th differences with n zeros prepended) gives row (n+3) of A182533, modulo signs and trailing zeros. - Travis Scott, Feb 19 2023

Programs

Formula

G.f.: 1 + 2*x + x^2.
a(n) = binomial(2n, n^2). - Wesley Ivan Hurt, Mar 08 2014

A241204 Expansion of (1 + 2*x)^2/(1 - 2*x)^2.

Original entry on oeis.org

1, 8, 32, 96, 256, 640, 1536, 3584, 8192, 18432, 40960, 90112, 196608, 425984, 917504, 1966080, 4194304, 8912896, 18874368, 39845888, 83886080, 176160768, 369098752, 771751936, 1610612736, 3355443200, 6979321856, 14495514624, 30064771072, 62277025792
Offset: 0

Views

Author

Keywords

Crossrefs

Subsequence of A008574.

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 41); Coefficients(R!((1+2*x)^2/(1-2*x)^2));
    
  • Maple
    A241204:= n->`if`(n=0, 1, 2^(n+2)*n); seq(A241204(n), n=0..20); # Wesley Ivan Hurt, Apr 22 2014
  • Mathematica
    Table[2^(n+2)*n + Boole[n==0], {n,0,40}] (* G. C. Greubel, Jun 07 2023 *)
    LinearRecurrence[{4,-4},{1,8,32},30] (* Harvey P. Dale, Jun 23 2025 *)
  • PARI
    Vec((2*x+1)^2/(2*x-1)^2 + O(x^100)) \\ Colin Barker, Apr 22 2014
    
  • Sage
    def A241204(i):
        if i==0: return 1
        else: return 2^(2+i)*i;
    [A241204(n) for n in (0..30)] # Bruno Berselli, Apr 23 2014

Formula

a(n) = 2^(2+n)*n for n>0. - Colin Barker, Apr 23 2014
a(n) = 4*a(n-1)-4*a(n-2) for n>2. - Colin Barker, Apr 23 2014
From Amiram Eldar, Jan 13 2021: (Start)
Sum_{n>=1} 1/a(n) = log(2)/4.
Sum_{n>=1} (-1)^(n+1)/a(n) = log(3/2)/4. (End)
E.g.f.: 1 + 8*x*exp(x). - G. C. Greubel, Jun 07 2023

A250123 Coordination sequence of point of type 3.3.4.3.4 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.

Original entry on oeis.org

1, 5, 8, 8, 11, 17, 25, 27, 24, 30, 38, 46, 47, 44, 46, 50, 64, 68, 65, 66, 70, 80, 80, 83, 87, 91, 100, 100, 99, 99, 109, 121, 121, 119, 119, 125, 133, 139, 140, 140, 145, 153, 155, 152, 158, 166, 174, 175, 172, 174, 178, 192, 196, 193, 194, 198, 208, 208, 211
Offset: 0

Views

Author

N. J. A. Sloane, Nov 29 2014

Keywords

Comments

This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.

Crossrefs

List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706(3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120 (3.3.3.3.6), A250122 (3.12.12).

Formula

Empirical g.f.: -(x+1)*(x^15 +3*x^14 -4*x^11 -6*x^10 -7*x^9 -4*x^8 -7*x^7 -11*x^6 -9*x^5 -7*x^4 -4*x^3 -4*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014

Extensions

Galebach link from Joseph Myers, Nov 30 2014
Extended by Joseph Myers, Dec 02 2014

A250124 Coordination sequence of point of type 3.3.12.4 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.

Original entry on oeis.org

1, 4, 7, 10, 15, 16, 21, 29, 28, 34, 33, 40, 48, 45, 53, 51, 59, 65, 64, 72, 68, 78, 83, 83, 89, 87, 97, 100, 102, 107, 106, 114, 119, 121, 124, 125, 132, 138, 138, 143, 144, 149, 157, 156, 162, 161, 168, 176, 173, 181, 179, 187, 193, 192, 200, 196, 206, 211, 211
Offset: 0

Views

Author

N. J. A. Sloane, Nov 29 2014

Keywords

Comments

This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.

Crossrefs

List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706(3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120 (3.3.3.3.6), A250122 (3.12.12).

Formula

Empirical g.f.: -(3*x^14 -4*x^12 -4*x^11 -7*x^10 -12*x^9 -14*x^8 -21*x^7 -17*x^6 -15*x^5 -15*x^4 -10*x^3 -7*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014

Extensions

Galebach link from Joseph Myers, Nov 30 2014
Extended by Joseph Myers, Dec 02 2014

A250125 Coordination sequence of point of type 3.4.3.12 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.

Original entry on oeis.org

1, 4, 6, 11, 13, 15, 23, 23, 33, 30, 33, 42, 41, 54, 46, 54, 58, 58, 73, 64, 75, 74, 79, 89, 81, 94, 92, 100, 105, 102, 110, 109, 119, 123, 123, 126, 130, 135, 140, 142, 144, 151, 151, 161, 158, 161, 170, 169, 182, 174, 182, 186, 186, 201, 192, 203, 202, 207, 217
Offset: 0

Views

Author

N. J. A. Sloane, Nov 29 2014

Keywords

Comments

This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.

Crossrefs

List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706(3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120 (3.3.3.3.6), A250122 (3.12.12).

Formula

Empirical g.f.: -(x^17 +x^16 +x^15 +x^14 -2*x^13 -4*x^12 -6*x^11 -7*x^10 -11*x^9 -18*x^8 -16*x^7 -19*x^6 -14*x^5 -13*x^4 -11*x^3 -6*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014

Extensions

Galebach link from Joseph Myers, Nov 30 2014
Extended by Joseph Myers, Dec 02 2014

A250126 Coordination sequence of point of type 3.3.4.12 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.

Original entry on oeis.org

1, 4, 9, 9, 12, 19, 21, 28, 27, 31, 38, 40, 48, 44, 49, 56, 57, 67, 63, 69, 73, 75, 85, 80, 88, 92, 95, 102, 98, 106, 109, 114, 121, 118, 123, 127, 132, 138, 137, 142, 147, 149, 156, 155, 159, 166, 168, 176, 172, 177, 184, 185, 195, 191, 197, 201, 203, 213, 208
Offset: 0

Views

Author

N. J. A. Sloane, Nov 29 2014

Keywords

Comments

This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).

References

  • Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.

Crossrefs

List of coordination sequences for uniform planar nets: A008458 (the planar net 3.3.3.3.3.3), A008486 (6^3), A008574 (4.4.4.4 and 3.4.6.4), A008576 (4.8.8), A008579 (3.6.3.6), A008706(3.3.3.4.4), A072154 (4.6.12), A219529 (3.3.4.3.4), A250120 (3.3.3.3.6), A250122 (3.12.12).

Formula

Empirical g.f.: -(2*x^16 +x^14 -2*x^12 -7*x^11 -10*x^10 -10*x^9 -14*x^8 -18*x^7 -17*x^6 -18*x^5 -12*x^4 -9*x^3 -9*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014

Extensions

Galebach link from Joseph Myers, Nov 30 2014
Extended by Joseph Myers, Dec 02 2014

A322038 Irregular triangle read by rows: for n >= 0, row n gives the coordination sequence for the tiling of a flat torus by a square grid with n points along each circuit.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 4, 4, 1, 4, 6, 4, 1, 1, 4, 8, 8, 4, 1, 4, 8, 10, 8, 4, 1, 1, 4, 8, 12, 12, 8, 4, 1, 4, 8, 12, 14, 12, 8, 4, 1, 1, 4, 8, 12, 16, 16, 12, 8, 4, 1, 4, 8, 12, 16, 18, 16, 12, 8, 4, 1, 1, 4, 8, 12, 16, 20, 20, 16, 12, 8, 4
Offset: 0

Views

Author

N. J. A. Sloane, Dec 01 2018

Keywords

Comments

More precisely, this is the coordination sequence for the quotient graph Z^2 / (nZ X nZ). The graph has n^2 vertices.
There are obvious generalizations: for example, Z^2 / (mZ X nZ) where m and n are not necessarily equal.

Examples

			The triangle begins:
1,
1,
1, 2, 1,
1, 4, 4,
1, 4, 6, 4, 1,
1, 4, 8, 8, 4,
1, 4, 8, 10, 8, 4, 1,
1, 4, 8, 12, 12, 8, 4,
1, 4, 8, 12, 14, 12, 8, 4, 1,
1, 4, 8, 12, 16, 16, 12, 8, 4,
1, 4, 8, 12, 16, 18, 16, 12, 8, 4, 1,
...
		

Crossrefs

The rows converge to A008574.

Formula

Since the underlying graphs are finite, the coordination sequences are polynomial P_n(x).
For n even, P_n(x) = (1+x)^2*(Sum_{i=0..(n-2)/2} x^i)^2;
for n odd, P_n(x) = (1 + 2*Sum_{i=0..(n-1)/2} x^i)^2.

A343599 T(n,k) is the coordination number of the (n+1)-dimensional cubic lattice for radius k; triangle read by rows, n>=0, 0<=k<=n.

Original entry on oeis.org

1, 1, 4, 1, 6, 18, 1, 8, 32, 88, 1, 10, 50, 170, 450, 1, 12, 72, 292, 912, 2364, 1, 14, 98, 462, 1666, 4942, 12642, 1, 16, 128, 688, 2816, 9424, 27008, 68464, 1, 18, 162, 978, 4482, 16722, 53154, 148626, 374274, 1, 20, 200, 1340, 6800, 28004, 97880, 299660, 822560, 2060980, 1, 22, 242, 1782, 9922, 44726, 170610, 568150, 1690370, 4573910, 11414898
Offset: 0

Views

Author

R. J. Mathar, Apr 21 2021

Keywords

Examples

			The full array starts
     1      2      2      2      2      2      2      2      2
     1      4      8     12     16     20     24     28     32
     1      6     18     38     66    102    146    198    258
     1      8     32     88    192    360    608    952   1408
     1     10     50    170    450   1002   1970   3530   5890
     1     12     72    292    912   2364   5336  10836  20256
     1     14     98    462   1666   4942  12642  28814  59906
     1     16    128    688   2816   9424  27008  68464 157184
     1     18    162    978   4482  16722  53154 148626 374274
		

Crossrefs

Cf. A035607 (by antidiags), A008574 (n=1), A005899 (n=2), A008412 (n=3), A008413 (n=4), A008414 (n=5), A001105 (k=2), A035597 (k=3), A035598 (k=4).
Main diagonal gives A050146(n+1).

Programs

  • Maple
    A343599 := proc(n,k)
        local g,x,y ;
        g := (1+y)/(1-x-y-x*y) ;
        coeftayl(%,x=0,n) ;
        coeftayl(%,y=0,k) ;
    end proc:
  • Mathematica
    T[n_, k_] := Module[{x, y}, SeriesCoefficient[(1 + y)/(1 - x - y - x*y), {x, 0, n}] // SeriesCoefficient[#, {y, 0, k}]&];
    Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Aug 16 2023 *)

Formula

G.f.: (1+y)/(1-x-y-x*y).
T(n,k) = A008288(n,k) + A008288(n,k-1).

A058394 A square array based on natural numbers (A000027) with each term being the sum of 2 consecutive terms in the previous row.

Original entry on oeis.org

1, 0, 1, 2, 1, 1, 0, 2, 2, 1, 3, 2, 3, 3, 1, 0, 3, 4, 5, 4, 1, 4, 3, 5, 7, 8, 5, 1, 0, 4, 6, 9, 12, 12, 6, 1, 5, 4, 7, 11, 16, 20, 17, 7, 1, 0, 5, 8, 13, 20, 28, 32, 23, 8, 1, 6, 5, 9, 15, 24, 36, 48, 49, 30, 9, 1, 0, 6, 10, 17, 28, 44, 64, 80, 72, 38, 10, 1, 7, 6, 11, 19, 32, 52, 80, 112, 129
Offset: 0

Views

Author

Henry Bottomley, Nov 24 2000

Keywords

Comments

Changing the formula by replacing T(2n,0)=T(n,2) by T(2n,0)=T(n,m) for some other value of m, would make the generating function change to coefficient of x^n in expansion of (1+x)^k/(1-x^2)^m. This would produce A058393, A058395, A057884 (and effectively A007318).

Examples

			Rows are (1,0,2,0,3,0,4,...), (1,1,2,2,3,3,...), (1,2,3,4,5,6,...), (1,3,5,7,9,11,...), etc.
		

Crossrefs

Rows are A027656 (A000027 with zeros), A008619, A000027, A005408, A008574 etc. Columns are A000012, A001477, A022856 etc. Diagonals include A034007, A045891, A045623, A001792, A001787, A000337, A045618, A045889, A034009, A055250, A055251 etc. The triangle A055249 also appears in half of the array.

Formula

T(n, k)=T(n-1, k-1)+T(n, k-1) with T(0, k)=1, T(2n, 0)=T(n, 2) and T(2n+1, 0)=0. Coefficient of x^n in expansion of (1+x)^k/(1-x^2)^2.

A179000 Array T(n,k) read by antidiagonals: coefficient [x^k] of (1 + n*Sum_{i>=1} x^i)^2, k >= 0.

Original entry on oeis.org

1, 1, 2, 1, 4, 3, 1, 6, 8, 4, 1, 8, 15, 12, 5, 1, 10, 24, 24, 16, 6, 1, 12, 35, 40, 33, 20, 7, 1, 14, 48, 60, 56, 42, 24, 8, 1, 16, 63, 84, 85, 72, 51, 28, 9, 1, 18, 80, 112, 120, 110, 88, 60, 32, 10
Offset: 1

Views

Author

Gary W. Adamson, Jan 03 2011

Keywords

Comments

Antidiagonal sums are in A136396.

Examples

			First few rows of the array:
  1   2   3   4   5   6   7   8   9  10  11  A000027
  1   4   8  12  16  20  24  28  32  36  40  A008574
  1   6  15  24  33  42  51  60  69  78  87  A122709
  1   8  24  40  56  72  88 104 120 136 152  A051062
  1  10  35  60  85 110 135 160 185 210 235
  1  12  48  84 120 156 192 228 264 300 336
  1  14  63 112 161 210 259 308 357 406 455
  1  16  80 144 208 272 336 400 464 528 592
  1  18  99 180 261 342 423 504 585 666 747
Row n=3 is generated by (1 + 3x + 3x^2 + 3x^3 + 3x^4 + ...)^2 = 1 + 6x + 15x^2 + 24x^3 + ..., for example.
		

Crossrefs

Programs

  • Maple
    A179000 := proc(n,k) if k = 0 then 1; else 2*n+n^2*(k-1) ; end if; end proc: # R. J. Mathar, Jan 05 2011

Formula

T(n,0) = 1; T(n,k) = n*(2+n*(k-1)), k > 0. - R. J. Mathar, Jan 05 2011
Previous Showing 91-100 of 124 results. Next