A053220 -id:A053220 - cp's OEIS frontend

A236538 Triangle read by rows: T(n,k) = (n+1)2^(n-2)+(k-1)2^(n-1) for 1 <= k <= n.

1, 3, 5, 8, 12, 16, 20, 28, 36, 44, 48, 64, 80, 96, 112, 112, 144, 176, 208, 240, 272, 256, 320, 384, 448, 512, 576, 640, 576, 704, 832, 960, 1088, 1216, 1344, 1472, 1280, 1536, 1792, 2048, 2304, 2560, 2816, 3072, 3328, 2816, 3328, 3840, 4352, 4864, 5376

Offset: 1

Fedor Igumnov, Jan 28 2014

1, 9, 45, 161, 497, 1409, ... is the sequence of perimeters (sum of border elements) of the triangle.
1, 5, 80, 3520, 394240, 107233280, 68629299200, ... is the sequence of determinants of the triangle.
Only the first three terms are odd.

			Triangle begins:
================================================
\k |    1     2     3     4     5     6     7
n\ |
================================================
1  |    1;
2  |    3,    5;
3  |    8,   12,   16;
4  |   20,   28,   36,   44;
5  |   48,   64,   80,   96,  112;
6  |  112,  144,  176,  208,  240,  272;
7  |  256,  320,  384,  448,  512,  576,  640;
...

Fedor Igumnov, T(n,k) for n = 1..26

Cf. A001792 (column 1), A053220 (right border). Also:
A014477, row sums;
A036826, partial sums;
A058962, central elements in odd rows;
A045623, second column;
A045891, third column;
A034007, fourth column;
A167667, subdiagonal;
A130129, second subdiagonal.

int a(int n, int k) {return (n+1)*pow(2,n-2)+(k-1)*pow(2,n-1);}

/* As triangle: */ [[(n+1)*2^(n-2)+(k-1)*2^(n-1): k in [1..n]]: n in [1..10]]; // Bruno Berselli, Jan 28 2014

t[n_, k_] := (n + 1)*2^(n - 2) + (k - 1)*2^(n - 1); Table[t[n, k], {n, 10}, {k, n}] // Flatten (* Bruno Berselli, Jan 28 2014 *)

T(n,k) = T(n-1,k) + T(n-1,k+1).

Sum_{k=1..n} T(n,k) = n^2*2^(n-1) = A014477(n-1).

More terms from Bruno Berselli, Jan 28 2014

A347823 Triangle read by rows: T(n,k) = (n+k+1)*binomial(n,k), 0 <= k <= n.

Original entry on oeis.org

1, 2, 3, 3, 8, 5, 4, 15, 18, 7, 5, 24, 42, 32, 9, 6, 35, 80, 90, 50, 11, 7, 48, 135, 200, 165, 72, 13, 8, 63, 210, 385, 420, 273, 98, 15, 9, 80, 308, 672, 910, 784, 420, 128, 17, 10, 99, 432, 1092, 1764, 1890, 1344, 612, 162, 19, 11, 120, 585, 1680, 3150, 4032, 3570, 2160, 855, 200, 21

Offset: 0

Jules Beauchamp, Jan 23 2022

			Triangle begins:
  1;
  2,  3;
  3,  8,   5;
  4, 15,  18,   7;
  5, 24,  42,  32,   9;
  6, 35,  80,  90,  50,  11;
  7, 48, 135, 200, 165,  72, 13;
  8, 63, 210, 385, 420, 273, 98, 15;
  ...

Andrew Howroyd, Table of n, a(n) for n = 0..1325 (rows 0..50)

Row sums give A053220.
Columns give A000027, A005563, A212343.
Diagonals give A005408, A001105, A059270, A112742.
Cf. A007318, A094727.

T(n,k) = (n+k+1)*binomial(n,k) \\ Andrew Howroyd, Jan 23 2022

T(n,k) = A094727(n+1,k)*A007318(n,k).

Row g.f.: (1 + x)^(n-1)*(1 + n + x + 2*n*x). - Stefano Spezia, Jan 23 2022

A367631 Triangle read by rows: T(n,k) is the number of permutations of length n avoiding simultaneously the patterns 123 and 132 with the maximum number of non-overlapping descents equal k.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 0, 4, 0, 0, 0, 5, 3, 0, 0, 0, 2, 14, 0, 0, 0, 0, 0, 23, 9, 0, 0, 0, 0, 0, 16, 48, 0, 0, 0, 0, 0, 0, 4, 97, 27, 0, 0, 0, 0, 0, 0, 0, 94, 162, 0, 0, 0, 0, 0, 0, 0, 0, 44, 387, 81, 0, 0, 0, 0, 0, 0, 0, 0, 8, 476, 540, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 320, 1485, 243, 0, 0, 0, 0, 0, 0

Offset: 0

Tian Han, Nov 24 2023

Number of permutations of length n avoiding simultaneously the patterns 123 and 132 with the maximum number of non-overlapping descents equal k. A descent in a permutation a(1)a(2)...a(n) is position i such that a(i) > a(i+1).

			Triangle T(n,k) begins:
  1;
  1, 0;
  1, 1,  0;
  0, 4,  0,  0;
  0, 5,  3,  0,   0;
  0, 2, 14,  0,   0,    0;
  0, 0, 23,  9,   0,    0,   0;
  0, 0, 16, 48,   0,    0,   0, 0;
  0, 0,  4, 97,  27,    0,   0, 0, 0;
  0, 0,  0, 94, 162,    0,   0, 0, 0, 0;
  0, 0,  0, 44, 387,   81,   0, 0, 0, 0, 0;
  0, 0,  0,  8, 476,  540,   0, 0, 0, 0, 0, 0;
  0, 0,  0,  0, 320, 1485, 243, 0, 0, 0, 0, 0, 0;
  ...

Tian Han and Sergey Kitaev, Joint distributions of statistics over permutations avoiding two patterns of length 3, arXiv:2311.02974 [math.CO], 2023. See formula 7 at page 7.

Row sums give A011782.
Column sums give 3*A005054.
T(2n,n) gives A133494.
T(3n+2,n) gives A000079.
T(3n+1,n) gives A053220(n+1).

G.f.: (1 + x + x^2 - 2*x^2*z - x^3*z)/(1 - 3*x^2*z - 2*x^3*z).

A340228 a(n) is the sum of the lengths of all the segments used to draw a rectangle of height 2^(n-1) and width n divided into 2^(n-1) rectangles of unit height, in turn, divided into rectangles of unit height and lengths corresponding to the parts of the compositions of n.

Original entry on oeis.org

4, 11, 27, 64, 149, 342, 775, 1736, 3849, 8458, 18443, 39948, 86029, 184334, 393231, 835600, 1769489, 3735570, 7864339, 16515092, 34603029, 72351766, 150994967, 314572824, 654311449, 1358954522, 2818572315, 5838471196, 12079595549, 24964497438, 51539607583, 106300440608

Offset: 1

Stefano Spezia, Jan 01 2021

			Illustrations for n = 1..4:
      _           _ _
     |_|         |_ _|
                 |_|_|
  a(1) = 4     a(2) = 11
    _ _ _       _ _ _ _
   |_ _ _|     |_ _ _ _|
   |_ _|_|     |_ _ _|_|
   |_|_ _|     |_|_ _ _|
   |_|_|_|     |_ _|_ _|
               |_ _|_|_|
               |_|_ _|_|
               |_|_|_ _|
               |_|_|_|_|
  a(3) = 27    a(4) = 64

Index entries for linear recurrences with constant coefficients, signature (6,-13,12,-4).
Index entries for sequences related to compositions.

Cf. A000079, A001792, A006127, A011782, A045623, A053220, A188626, A215149, A228525.

Cf. A338969.

LinearRecurrence[{6,-13,12,-4},{4,11,27,64},32]

O.g.f.: x*(4 - 13*x + 13*x^2 - 3*x^3)/(1 - 3*x + 2*x^2)^2.
E.g.f.: (exp(2*x)*(3 + 6*x) + 4*x*exp(x) - 3)/4.
a(n) = 6*a(n-1) - 13*a(n-2) + 12*a(n-3) - 4*a(n-4) for n > 4.
a(n) = n + 3*(n + 1)*2^(n-2).
a(n) = A001792(n) + A188626(n).
a(n) = A045623(n) + A215149(n).
a(n) = A006127(n) + A053220(n).

A386250 Total number of ones in runs of 1's of length >= 4 over all binary strings of length n.

Original entry on oeis.org

0, 0, 0, 0, 4, 13, 36, 92, 224, 528, 1216, 2752, 6144, 13568, 29696, 64512, 139264, 299008, 638976, 1359872, 2883584, 6094848, 12845056, 27000832, 56623104, 118489088, 247463936, 515899392, 1073741824, 2231369728, 4630511616, 9596567552, 19864223744, 41070624768, 84825604096, 175019917312

Offset: 0

Félix Balado, Aug 14 2025

			For n=6 there are eight binary strings that contain runs of 1s of length >= 4: 001111, 011110, 011111, 101111, 111100, 111101, 111110 and 111111; the runs of length >= 4 in these strings contain a(6) = 36 ones.

Index entries for linear recurrences with constant coefficients, signature (4,-4).

Cf. A001787, A066373, A128135, A053220.

LinearRecurrence [{4,-4}, {4,13}, 30] (* Hugo Pfoertner, Aug 14 2025 *)

For n>=4, a(n) = (5*n-12)*2^(n-5).

G.f.: -x^4*(3*x-4)/(2*x-1)^2. - Alois P. Heinz, Aug 14 2025

cp's OEIS Frontend

A236538 Triangle read by rows: T(n,k) = (n+1)*2^(n-2)+(k-1)*2^(n-1) for 1 <= k <= n.

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A347823 Triangle read by rows: T(n,k) = (n+k+1)*binomial(n,k), 0 <= k <= n.

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A367631 Triangle read by rows: T(n,k) is the number of permutations of length n avoiding simultaneously the patterns 123 and 132 with the maximum number of non-overlapping descents equal k.

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A340228 a(n) is the sum of the lengths of all the segments used to draw a rectangle of height 2^(n-1) and width n divided into 2^(n-1) rectangles of unit height, in turn, divided into rectangles of unit height and lengths corresponding to the parts of the compositions of n.

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A386250 Total number of ones in runs of 1's of length >= 4 over all binary strings of length n.

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A236538 Triangle read by rows: T(n,k) = (n+1)2^(n-2)+(k-1)2^(n-1) for 1 <= k <= n.