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.

A386932 Lexicographically earliest sequence of distinct positive integers that can be partitioned into runs of integers without common bits, the n-th such run having a(n) terms.

Original entry on oeis.org

1, 2, 4, 3, 8, 16, 32, 5, 10, 48, 6, 9, 64, 128, 256, 512, 1024, 2048, 7, 24, 96, 384, 1536, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 11, 20, 160, 320, 2560, 5120, 24576, 98304, 393216, 1572864, 6291456, 8388608
Offset: 1

Views

Author

Rémy Sigrist, Aug 09 2025

Keywords

Comments

This sequence is a permutation of the positive integers as each run starts with the least integer not yet in the sequence.
The powers of two appear in natural order.

Examples

			The first terms and runs are:
  n  a(n)  n-th run
  -  ----  -----------------------------------
  1     1  1
  2     2  2, 4
  3     4  3, 8, 16, 32
  4     3  5, 10, 48
  5     8  6, 9, 64, 128, 256, 512, 1024, 2048
		

Crossrefs

See A385661 for a similar sequence.
Cf. A358875, A387024 (inverse).

Programs

  • PARI
    \\ See Links section.

A367177 Triangle read by rows, T(n, k) = [x^k] hypergeom([1/2, -n, -n], [1, 1], 4*x).

Original entry on oeis.org

1, 1, 2, 1, 8, 6, 1, 18, 54, 20, 1, 32, 216, 320, 70, 1, 50, 600, 2000, 1750, 252, 1, 72, 1350, 8000, 15750, 9072, 924, 1, 98, 2646, 24500, 85750, 111132, 45276, 3432, 1, 128, 4704, 62720, 343000, 790272, 724416, 219648, 12870
Offset: 0

Views

Author

Peter Luschny, Nov 07 2023

Keywords

Examples

			Triangle T(n, k) starts:
  [0] 1;
  [1] 1,   2;
  [2] 1,   8,    6;
  [3] 1,  18,   54,     20;
  [4] 1,  32,  216,    320,      70;
  [5] 1,  50,  600,   2000,    1750,     252;
  [6] 1,  72, 1350,   8000,   15750,    9072,     924;
  [7] 1,  98, 2646,  24500,   85750,  111132,   45276,    3432;
  [8] 1, 128, 4704,  62720,  343000,  790272,  724416,  219648,   12870;
  [9] 1, 162, 7776, 141120, 1111320, 4000752, 6519744, 4447872, 1042470, 48620;
		

Crossrefs

Cf. A002893 (row sum), A002897 (central column), A000984 (main diagonal).

Programs

  • Maple
    p := n -> hypergeom([1/2, -n, -n], [1, 1], 4*x):
    T := (n, k) -> coeff(simplify(p(n)), x, k):
    seq(seq(T(n, k), k = 0..n), n = 0..9);

Formula

T(n, k) = binomial(n, k)^2 * binomial(2*k, k).

A367025 Triangle read by rows, T(n, k) = [x^k] p(n), where p(n) = (1 - hypergeom([-1/2, -n - 1, -n - 1], [1, 1], 4*x)) / (2*x).

Original entry on oeis.org

1, 4, 1, 9, 9, 2, 16, 36, 32, 5, 25, 100, 200, 125, 14, 36, 225, 800, 1125, 504, 42, 49, 441, 2450, 6125, 6174, 2058, 132, 64, 784, 6272, 24500, 43904, 32928, 8448, 429, 81, 1296, 14112, 79380, 222264, 296352, 171072, 34749, 1430
Offset: 0

Views

Author

Peter Luschny, Nov 07 2023

Keywords

Examples

			Triangle T(n, k) starts:
  [0]   1;
  [1]   4,    1;
  [2]   9,    9,     2;
  [3]  16,   36,    32,      5;
  [4]  25,  100,   200,    125,     14;
  [5]  36,  225,   800,   1125,    504,      42;
  [6]  49,  441,  2450,   6125,   6174,    2058,     132;
  [7]  64,  784,  6272,  24500,  43904,   32928,    8448,    429;
  [8]  81, 1296, 14112,  79380, 222264,  296352,  171072,  34749,   1430;
  [9] 100, 2025, 28800, 220500, 889056, 1852200, 1900800, 868725, 143000, 4862;
		

Crossrefs

Cf. A000290 (first column), A000108 (main diagonal).

Programs

  • Maple
    p := n -> (1 - hypergeom([-1/2, -n-1, -n-1], [1, 1], 4*x)) / (2*x):
    T := (n, k) -> coeff(simplify(p(n)), x, k):
    seq(seq(T(n, k), k = 0..n), n = 0..9);
  • Mathematica
    T[n_,k_]:=Binomial[n+1,n-k]^2*Binomial[2*k,k]/(k+1);Flatten[Table[T[n,k],{n,0,9},{k,0,n}]] (* Detlef Meya, Nov 19 2023 *)

Formula

T(n,k) = binomial(n+1,n-k)^2*binomial(2*k,k)/(k+1). - Detlef Meya, Nov 19 2023

A367178 Triangle read by rows. T(n, k) = binomial(n, k)^2 * CatalanNumber(k).

Original entry on oeis.org

1, 1, 1, 1, 4, 2, 1, 9, 18, 5, 1, 16, 72, 80, 14, 1, 25, 200, 500, 350, 42, 1, 36, 450, 2000, 3150, 1512, 132, 1, 49, 882, 6125, 17150, 18522, 6468, 429, 1, 64, 1568, 15680, 68600, 131712, 103488, 27456, 1430, 1, 81, 2592, 35280, 222264, 666792, 931392, 555984, 115830, 4862
Offset: 0

Views

Author

Peter Luschny, Nov 07 2023

Keywords

Examples

			Triangle T(n, k) starts:
  [0] 1;
  [1] 1,  1;
  [2] 1,  4,    2;
  [3] 1,  9,   18,     5;
  [4] 1, 16,   72,    80,     14;
  [5] 1, 25,  200,   500,    350,     42;
  [6] 1, 36,  450,  2000,   3150,   1512,    132;
  [7] 1, 49,  882,  6125,  17150,  18522,   6468,    429;
  [8] 1, 64, 1568, 15680,  68600, 131712, 103488,  27456,   1430;
  [9] 1, 81, 2592, 35280, 222264, 666792, 931392, 555984, 115830, 4862;
		

Crossrefs

Cf. A086618 (row sums), A186415 (central column), A000108 (main diagonal).

Programs

  • Maple
    T := (n, k) -> binomial(n, k)^2 * binomial(2*k, k) / (k + 1):
    seq(seq(T(n, k), k = 0..n), n = 0..9);

Formula

T(n, k) = binomial(n, k)^2 * binomial(2*k, k) / (k + 1).
T(n, k) = [x^n] hypergeom([1/2, -n, -n], [1, 2], 4*x).
Showing 1-4 of 4 results.