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.

Previous Showing 11-19 of 19 results.

A317494 Triangle read by rows: T(0,0) = 1; T(n,k) = T(n-1,k) + 2 * T(n-3,k-1) for k = 0..floor(n/3); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 4, 1, 6, 1, 8, 4, 1, 10, 12, 1, 12, 24, 1, 14, 40, 8, 1, 16, 60, 32, 1, 18, 84, 80, 1, 20, 112, 160, 16, 1, 22, 144, 280, 80, 1, 24, 180, 448, 240, 1, 26, 220, 672, 560, 32, 1, 28, 264, 960, 1120, 192, 1, 30, 312, 1320, 2016, 672, 1, 32, 364, 1760, 3360, 1792, 64
Offset: 0

Views

Author

Zagros Lalo, Jul 30 2018

Keywords

Comments

The numbers in rows of the triangle are along a "second layer" of skew diagonals pointing top-right in center-justified triangle given in A013609 ((1+2*x)^n) and along a "second layer" of skew diagonals pointing top-left in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-x-2*x^3) are given by the sequence generated by the row sums.
The row sums give A003229.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 1.695620769559862... (see A289265), when n approaches infinity.

Examples

			Triangle begins:
  1;
  1;
  1;
  1,  2;
  1,  4;
  1,  6;
  1,  8,   4;
  1, 10,  12;
  1, 12,  24;
  1, 14,  40,    8;
  1, 16,  60,   32;
  1, 18,  84,   80;
  1, 20, 112,  160,   16;
  1, 22, 144,  280,   80;
  1, 24, 180,  448,  240;
  1, 26, 220,  672,  560,   32;
  1, 28, 264,  960, 1120,  192;
  1, 30, 312, 1320, 2016,  672;
  1, 32, 364, 1760, 3360, 1792, 64;
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3, pp. 358, 359

Crossrefs

Programs

  • GAP
    Flat(List([0..20],n->List([0..Int(n/3)],k->2^k/(Factorial(n-3*k)*Factorial(k))*Factorial(n-2*k)))); # Muniru A Asiru, Jul 31 2018
  • Mathematica
    t[n_, k_] := t[n, k] = 2^k/((n - 3 k)! k!) (n - 2 k)!; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/3]} ] // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, t[n - 1, k] + 2 t[n - 3, k - 1]]; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/3]}] // Flatten

Formula

T(n,k) = 2^k / ((n - 3k)! k!) * (n - 2k)! where n is a nonnegative integer and k = 0..floor(n/3).

A317495 Triangle read by rows: T(0,0) = 1; T(n,k) =2 * T(n-1,k) + T(n-3,k-1) for k = 0..floor(n/3); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 2, 4, 8, 1, 16, 4, 32, 12, 64, 32, 1, 128, 80, 6, 256, 192, 24, 512, 448, 80, 1, 1024, 1024, 240, 8, 2048, 2304, 672, 40, 4096, 5120, 1792, 160, 1, 8192, 11264, 4608, 560, 10, 16384, 24576, 11520, 1792, 60, 32768, 53248, 28160, 5376, 280, 1, 65536, 114688, 67584, 15360, 1120, 12
Offset: 0

Views

Author

Zagros Lalo, Jul 30 2018

Keywords

Comments

The numbers in rows of the triangle are along a "second layer" of skew diagonals pointing top-left in center-justified triangle given in A013609 ((1+2*x)^n) and along a "second layer" of skew diagonals pointing top-right in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-2x-x^3) are given by the sequence generated by the row sums.
The row sums give A008998 and Pisot sequences E(4,9), P(4,9) when n > 1, see A020708.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 2.205569430400..., when n approaches infinity.

Examples

			Triangle begins:
       1;
       2;
       4;
       8,      1;
      16,      4;
      32,     12;
      64,     32,      1;
     128,     80,      6;
     256,    192,     24;
     512,    448,     80,      1;
    1024,   1024,    240,      8;
    2048,   2304,    672,     40;
    4096,   5120,   1792,    160,     1;
    8192,  11264,   4608,    560,    10;
   16384,  24576,  11520,   1792,    60;
   32768,  53248,  28160,   5376,   280,   1;
   65536, 114688,  67584,  15360,  1120,  12;
  131072, 245760, 159744,  42240,  4032,  84;
  262144, 524288, 372736, 112640, 13440, 448, 1;
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3, pp. 358, 359.

Crossrefs

Row sums give A008998, A020708.
Cf. A000079 (column 0), A001787 (column 1), A001788 (column 2), A001789 (column 3), A003472 (column 4).

Programs

  • GAP
    Flat(List([0..20],n->List([0..Int(n/3)],k->2^(n-3*k)/(Factorial(n-3*k)*Factorial(k))*Factorial(n-2*k)))); # Muniru A Asiru, Jul 31 2018
    
  • Magma
    /* As triangle */ [[2^(n-3*k)/(Factorial(n-3*k)*Factorial(k))* Factorial(n-2*k): k in [0..Floor(n/3)]]: n in [0.. 15]]; // Vincenzo Librandi, Sep 05 2018
  • Mathematica
    t[n_, k_] := t[n, k] = 2^(n - 3k)/((n - 3 k)! k!) (n - 2 k)!; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/3]} ]  // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, 2 t[n - 1, k] + t[n - 3, k - 1]]; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/3]}] // Flatten

Formula

T(n,k) = 2^(n - 3k) / ((n - 3k)! k!) * (n - 2k)! where n >= 0 and k = 0..floor(n/3).

A318775 Triangle read by rows: T(0,0) = 1; T(n,k) = T(n-1,k) + 2 * T(n-5,k-1) for k = 0..floor(n/5); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 2, 1, 4, 1, 6, 1, 8, 1, 10, 1, 12, 4, 1, 14, 12, 1, 16, 24, 1, 18, 40, 1, 20, 60, 1, 22, 84, 8, 1, 24, 112, 32, 1, 26, 144, 80, 1, 28, 180, 160, 1, 30, 220, 280, 1, 32, 264, 448, 16, 1, 34, 312, 672, 80, 1, 36, 364, 960, 240, 1, 38, 420, 1320, 560, 1, 40, 480, 1760, 1120
Offset: 0

Views

Author

Zagros Lalo, Sep 04 2018

Keywords

Comments

The numbers in rows of the triangle are along a "fourth layer" skew diagonals pointing top-right in center-justified triangle given in A013609 ((1+2*x)^n) and along a "fourth layer" skew diagonals pointing top-left in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-x-2*x^5) are given by the sequence generated by the row sums.
The row sums give A318777.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 1.4510850920547191..., when n approaches infinity.

Examples

			Triangle begins:
  1;
  1;
  1;
  1;
  1;
  1,  2;
  1,  4;
  1,  6;
  1,  8;
  1, 10;
  1, 12,   4;
  1, 14,  12;
  1, 16,  24;
  1, 18,  40;
  1, 20,  60;
  1, 22,  84,    8;
  1, 24, 112,   32;
  1, 26, 144,   80;
  1, 28, 180,  160;
  1, 30, 220,  280;
  1, 32, 264,  448,  16;
  1, 34, 312,  672,  80;
  1, 36, 364,  960, 240;
  1, 38, 420, 1320, 560;
  ...
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3.

Crossrefs

Row sums give A318777.

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = 2^k/((n - 5 k)! k!) (n - 4 k)!; Table[t[n, k], {n, 0, 24}, {k, 0, Floor[n/5]} ] // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, t[n - 1, k] + 2 t[n - 5, k - 1]]; Table[t[n, k], {n, 0, 24}, {k, 0, Floor[n/5]}] // Flatten

Formula

T(n,k) = 2^k / ((n - 5*k)! k!) * (n - 4*k)! where n >= 0 and 0 <= k <= floor(n/5).

A318776 Triangle read by rows: T(0,0) = 1; T(n,k) = 2*T(n-1,k) + T(n-5,k-1) for k = 0..floor(n/5); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 2, 4, 8, 16, 32, 1, 64, 4, 128, 12, 256, 32, 512, 80, 1024, 192, 1, 2048, 448, 6, 4096, 1024, 24, 8192, 2304, 80, 16384, 5120, 240, 32768, 11264, 672, 1, 65536, 24576, 1792, 8, 131072, 53248, 4608, 40, 262144, 114688, 11520, 160, 524288, 245760, 28160, 560, 1048576, 524288, 67584, 1792, 1, 2097152, 1114112, 159744, 5376, 10
Offset: 0

Views

Author

Zagros Lalo, Sep 04 2018

Keywords

Comments

The numbers in rows of the triangle are along a "fourth layer" skew diagonals pointing top-left in center-justified triangle given in A013609 ((1+2*x)^n) and along a "fourth layer" skew diagonals pointing top-right in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-2*x-x^5) are given by the sequence generated by the row sums.
The row sums give A098588.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 2.0559673967128..., when n approaches infinity.

Examples

			Triangle begins:
        1;
        2;
        4;
        8;
       16;
       32,       1;
       64,       4;
      128,      12;
      256,      32;
      512,      80;
     1024,     192,      1;
     2048,     448,      6;
     4096,    1024,     24;
     8192,    2304,     80;
    16384,    5120,    240;
    32768,   11264,    672,    1;
    65536,   24576,   1792,    8;
   131072,   53248,   4608,   40;
   262144,  114688,  11520,  160;
   524288,  245760,  28160,  560;
  1048576,  524288,  67584, 1792,  1;
  2097152, 1114112, 159744, 5376, 10;
  ...
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3.

Crossrefs

Row sums give A098588.
Cf. also A000079 (column 0), A001787 (column 1), A001788 (column 2), A001789 (column 3)

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = 2^(n - 5 k)/((n - 5 k)! k!) (n - 4 k)!; Table[t[n, k], {n, 0, 21}, {k, 0, Floor[n/5]} ] // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, 2 t[n - 1, k] + t[n - 5, k - 1]]; Table[t[n, k], {n, 0, 21}, {k, 0, Floor[n/5]}] // Flatten

Formula

T(n,k) = 2^(n - 5*k) / ((n - 5*k)! k!) * (n - 4*k)! where n >= 0 and 0 <= k <= floor(n/5).

A109767 Triangle T(n,k), 0 <= k <= n, defined by T(n,k) = 2^k*A001497(n,k).

Original entry on oeis.org

1, 2, 2, 12, 12, 4, 120, 120, 48, 8, 1680, 1680, 720, 160, 16, 30240, 30240, 13440, 3360, 480, 32, 665280, 665280, 302400, 80640, 13440, 1344, 64, 17297280, 17297280, 7983360, 2217600, 403200, 48384, 3584, 128, 518918400, 518918400
Offset: 0

Views

Author

Philippe Deléham, Aug 12 2005

Keywords

Comments

Also square array of unsigned coefficients of Hermite polynomials.
T[n,k]is A128099(2n,k)*A001813(n-k). - Richard Turk, Sep 26 2017

Examples

			Rows begin:
     1
     2,    2,
    12,   12,   4,
   120,  120,  48,   8,
  1680, 1680, 720, 160, 16,
Unsigned coefficients of Hermite polynomials:
     1,     2,      4,       8, ...
     2,    12,     48,     160, ...
    12,   120,    720,    3360, ...
   120,  1680,  13440,   80640, ...
  1680, 30240, 302400, 2217600, ...
		

Crossrefs

Cf. A001497.

Programs

  • Magma
    /* As triangle */ [[Factorial(2*n-k)*2^k/(Factorial(k)*Factorial(n-k)): k in [0..n]]: n in [0.. 10]]; // Vincenzo Librandi, Dec 14 2015
  • Maple
    seq(seq((2*n-k)!*2^k/(k!*(n-k)!),k=0..n),n=0..10); # Robert Israel, Sep 26 2017
  • Mathematica
    y[n_, x_] := Sqrt[2/(Pi*x)]*E^(1/x)*BesselK[-n-1/2, 1/x]; t[n_, k_] := 2^n*Coefficient[y[n, x], x, k]; Table[t[n, k], {n, 0, 8}, {k, n, 0, -1}] // Flatten (* or *) t[n_, k_] := (2*n - k)!*2^k/(k!*(n-k)!); Table[t[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* Jean-François Alcover, Mar 01 2013 *)
    Table[((2n-k)!*2^k)/(k!(n-k)!),{n,0,10},{k,0,n}]//Flatten (* Harvey P. Dale, Nov 23 2017 *)

Formula

T(n,k) = (2n-k)!*2^k/(k!*(n-k)!).

A317500 Triangle read by rows: T(0,0) = 1; T(n,k) = T(n-1,k) + 2 * T(n-4,k-1) for k = 0..floor(n/4); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 4, 1, 6, 1, 8, 1, 10, 4, 1, 12, 12, 1, 14, 24, 1, 16, 40, 1, 18, 60, 8, 1, 20, 84, 32, 1, 22, 112, 80, 1, 24, 144, 160, 1, 26, 180, 280, 16, 1, 28, 220, 448, 80, 1, 30, 264, 672, 240, 1, 32, 312, 960, 560, 1, 34, 364, 1320, 1120, 32
Offset: 0

Views

Author

Zagros Lalo, Sep 03 2018

Keywords

Comments

The numbers in rows of the triangle are along a "third layer" skew diagonals pointing top-right in center-justified triangle given in A013609 ((1+2*x)^n) and along a "third layer" skew diagonals pointing top-left in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-x-2*x^4) are given by the sequence generated by the row sums.
The row sums give A052942.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 1.543689012692076... (A256099: Decimal expansion of the real root of a cubic used by Omar Khayyám in a geometrical problem), when n approaches infinity.

Examples

			Triangle begins:
  1;
  1;
  1;
  1;
  1,  2;
  1,  4;
  1,  6;
  1,  8;
  1, 10,   4;
  1, 12,  12;
  1, 14,  24;
  1, 16,  40;
  1, 18,  60,   8;
  1, 20,  84,  32;
  1, 22, 112,  80;
  1, 24, 144, 160;
  1, 26, 180, 280,  16;
  1, 28, 220, 448,  80;
  1, 30, 264, 672, 240;
...
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3.

Crossrefs

Row sums give A052942.

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = 2^k/((n - 4 k)! k!) (n - 3 k)!; Table[t[n, k], {n, 0, 20}, {k, 0, Floor[n/4]} ] // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, t[n - 1, k] + 2 t[n - 4, k - 1]]; Table[t[n, k], {n, 0, 20}, {k, 0, Floor[n/4]}] // Flatten

Formula

T(n,k) = 2^k / ((n - 4*k)! k!) * (n - 3*k)! where n >= 0 and 0 <= k <= floor(n/4).

A317501 Triangle read by rows: T(0,0) = 1; T(n,k) = 2*T(n-1,k) + T(n-4,k-1) for k = 0..floor(n/4); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 2, 4, 8, 16, 1, 32, 4, 64, 12, 128, 32, 256, 80, 1, 512, 192, 6, 1024, 448, 24, 2048, 1024, 80, 4096, 2304, 240, 1, 8192, 5120, 672, 8, 16384, 11264, 1792, 40, 32768, 24576, 4608, 160, 65536, 53248, 11520, 560, 1, 131072, 114688, 28160, 1792, 10, 262144, 245760, 67584, 5376, 60
Offset: 0

Views

Author

Zagros Lalo, Sep 03 2018

Keywords

Comments

Unsigned version of the triangle in A317506.
The numbers in rows of the triangle are along a "third layer" skew diagonals pointing top-left in center-justified triangle given in A013609 ((1+2*x)^n) and along a "third layer" skew diagonals pointing top-right in center-justified triangle given in A038207 ((2+x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (1+2*x)^n and (2+x)^n are given in A128099 and A207538 respectively.)
The coefficients in the expansion of 1/(1-2*x-x^4) are given by the sequence generated by the row sums.
The row sums give A008999.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 2.106919340376..., when n approaches infinity.

Examples

			Triangle begins:
       1;
       2;
       4;
       8;
      16,      1;
      32,      4;
      64,     12;
     128,     32;
     256,     80,     1;
     512,    192,     6;
    1024,    448,    24;
    2048,   1024,    80;
    4096,   2304,   240,    1;
    8192,   5120,   672,    8;
   16384,  11264,  1792,   40;
   32768,  24576,  4608,  160;
   65536,  53248, 11520,  560,  1;
  131072, 114688, 28160, 1792, 10;
  262144, 245760, 67584, 5376, 60;
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3.

Crossrefs

Row sums give A008999.

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = 2^(n - 4 k)/((n - 4 k)! k!) (n - 3 k)!; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/4]} ] // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, 2 t[n - 1, k] + t[n - 4, k - 1]]; Table[t[n, k], {n, 0, 18}, {k, 0, Floor[n/4]}] // Flatten

Formula

T(n,k) = 2^(n - 4*k) / ((n - 4*k)! k!) * (n - 3*k)! where n >= 0 and 0 <= k <= floor(n/4).

A191897 Coefficients of the Z(n,x) polynomials; Z(0,x) = 1, Z(1,x) = x and Z(n,x) = x*Z(n-1,x) - 2*Z(n-2,x), n >= 2.

Original entry on oeis.org

1, 1, 0, 1, 0, -2, 1, 0, -4, 0, 1, 0, -6, 0, 4, 1, 0, -8, 0, 12, 0, 1, 0, -10, 0, 24, 0, -8, 1, 0, -12, 0, 40, 0, -32, 0, 1, 0, -14, 0, 60, 0, -80, 0, 16, 1, 0, -16, 0, 84, 0, -160, 0, 80, 0, 1, 0, -18, 0, 112, 0, -280, 0, 240, 0, -32
Offset: 0

Views

Author

Paul Curtz, Jun 19 2011

Keywords

Comments

The coefficients of the Z(n,x) polynomials by decreasing exponents, see the formulas, define this triangle.

Examples

			The first few rows of the coefficients of the Z(n,x) are
  1;
  1,    0;
  1,    0,   -2;
  1,    0,   -4,    0;
  1,    0,   -6,    0,    4;
  1,    0,   -8,    0,   12,    0;
  1,    0,  -10,    0,   24,    0,   -8;
  1,    0,  -12,    0,   40,    0,  -32,    0;
  1,    0,  -14,    0,   60,    0,  -80,    0,   16;
  1,    0,  -16,    0,   84,    0, -160,    0,   80,    0;
		

Crossrefs

Row sums: A107920(n+1). Main diagonal: A077966(n).
Z(n,x=1) = A107920(n+1), Z(n,x=2) = A009545(n+1),
Z(n,x=3) = A000225(n+1), Z(n,x=4) = A007070(n),
Z(n,x=5) = A107839(n), Z(n,x=6) = A154244(n),
Z(n,x=7) = A186446(n), Z(n,x=8) = A190975(n+1),
Z(n,x=9) = A190979(n+1), Z(n,x=10) = A190869(n+1).
Row sum without sign: A113405(n+1).

Programs

  • Maple
    nmax:=10: Z(0, x):=1 : Z(1, x):=x: for n from 2 to nmax do Z(n, x) := x*Z(n-1, x) - 2*Z(n-2, x) od: for n from 0 to nmax do for k from 0 to n do T(n, k) := coeff(Z(n, x), x, n-k) od: od: seq(seq(T(n, k), k=0..n), n=0..nmax); # Johannes W. Meijer, Jun 27 2011, revised Nov 29 2012
  • Mathematica
    a[n_, k_] := If[OddQ[k], 0, 2^(k/2)*Coefficient[ ChebyshevU[n, x/2], x, n-k]]; Flatten[ Table[ a[n, k], {n, 0, 10}, {k, 0, n}]] (* Jean-François Alcover, Aug 02 2012, from 2nd formula *)

Formula

Z(0,x) = 1, Z(1,x) = x and Z(n,x) = x*Z(n-1,x) - 2*Z(n-2,x), n >= 2.
a(n,k) = A077957(k) * A053119(n,k). - Paul Curtz, Sep 30 2011

Extensions

Edited and information added by Johannes W. Meijer, Jun 27 2011

A246047 Irregular triangle read by rows, of partial serial probabilities T(n,k)_{2,3} (see "comments" for definitions and explanation).

Original entry on oeis.org

1, 0, 2, 4, 4, 16, 8, 16, 48, 16, 96, 128, 64, 32, 384, 320, 512, 64, 1280, 256, 768, 2560, 128, 3840, 2560, 1792, 10240, 1024, 256, 10752, 15360, 4096, 35840, 12288, 512, 28672, 71680, 4096, 9216, 114688, 86016, 1024, 73728, 286720, 57344
Offset: 0

Views

Author

Bob Selcoe, Aug 26 2014

Keywords

Comments

Define "serial probability" as the probability that n will occur as a partial sum in an infinite sequence of numbers drawn randomly from set J = {j1,j2,..jz}, where 1 <= j1 < j2< ... < jz and z is the number of members in set J. Generally, serial probabilities are found by the recurrence equation: a(n) = (z^(j1-1)*a(n-j1) + z^(j2-1)*a(n-j2) + z^(j3-1)*a(n-j3) + ... + z^(jz-1)*a(n-jz))/z^n, where a(0)=1 and a(n)=0 when n < 0.
Denote the recurrence sequence for set J as S(n){J}, and denote serial probability (P) for set J as P(n){J}, such that P = S(n){J}/z^n. For example, S(n){2,3} = 2*a(n-2) + 4*a(n-3); therefore P(n)A176739(n)/2%5En;%20so%20for%20example,%20since%20A176739(9)%20=%20192,%20the%20probability%20that%209%20will%20occur%20as%20a%20partial%20sum%20in%20a%20randomly-generated%20infinite%20sequence%20of%202s%20and%203s%20is%20192/512%20=%203/8.%20That%20is,%20P(9)">{2,3} = (2*a(n-2) + 4*a(n-3))/2^n. This also is equivalent to A176739(n)/2^n; so for example, since A176739(9) = 192, the probability that 9 will occur as a partial sum in a randomly-generated infinite sequence of 2s and 3s is 192/512 = 3/8. That is, P(9){2,3} = 3/8.
Define "partial serial probability" (P'') as the probability that n would occur given the different ways to sort the compositions (ordered partitions) of n into j1's..jz's; and let T(n,k){J} be the triangle of partial serial probabilities for set J, such that P'' = T(n,k){J}/z^n. Denote these probabilities as P''(n,k)_{J}.
This triangle therefore is T(n,k){2,3}, and P''(n,k){2,3} = T(n,k)_{2,3}/2^n.
In general, row sums of T(n,k){J} are S(n){J}; thus, the row sums of T(n,k)A176739(n)%20and%20sums%20of%20P''(n,k)">{2,3} are A176739(n) and sums of P''(n,k){2,3} are A176739(n)/2^n.
For T(n,k)A176739(9)%20=%20192,%20the%20probability%20that%209%20will%20occur%20as%20a%20partial%20sum%20with%20three%20sorts%20of%202s%20and%20one%20sort%20of%203s%20is%20128/512%20=%201/4%20(n=9,%20k=0),%20and%20with%20zero%20sorts%20of%202s%20and%20three%20sorts%20of%203s%20is%2064/512%20=%201/8%20(n=9,%20k=1),%20totaling%20192/512%20=%203/8.%20That%20is,%20P''(9,0)">{2,3}: there are [(n-3*(n mod 2)-6k)/2] sorts of 2s, and [2k+(n mod 2)] sorts of 3s. So taking again example A176739(9) = 192, the probability that 9 will occur as a partial sum with three sorts of 2s and one sort of 3s is 128/512 = 1/4 (n=9, k=0), and with zero sorts of 2s and three sorts of 3s is 64/512 = 1/8 (n=9, k=1), totaling 192/512 = 3/8. That is, P''(9,0){2,3} = 1/4 and P''(9,1)_{2,3} = 1/8.
Given n, maximum k for T(n,k)_{2,3} is A103221(n)-1. That is, row lengths are floor(n/6)+1 unless n == 1 (mod 6); if n == 1 (mod 6), row length is floor(n/6).

Examples

			Triangle starts:
     1;
     0;
     2;
     4;
     4;
    16;
     8,    16;
    48;
    16,    96;
   128,    64;
    32,   384;
   320,   512;
    64,  1280,  256;
   768,  2560;
   128,  3840, 2560;
  1792, 10240, 1024;
E.g., T(13,0) = 768 because 768/2^13 (3/32) is the probability that 13 will occur as a partial sum in a randomly-generated infinite sequence of 2s and 3s, where the compositions of 13 are into five sorts of 2s and one sort of 3s. In other words, P''(13,0)_{2,3} = 3/32. The sorts are 5 and 1, respectively, because (13 - 3*(13 mod 2) - 6*0)/2 = 5 and 2*0 + (13 mod 2) = 1.
		

Crossrefs

Cf. A176739, A007318 (binomial(n,k)), A103221, A128099 (related sequence).

Programs

  • PARI
    tabf(nn) = {for (n=0, nn, for (k=0, max(0, (n+2)\2 - (n+2)\3 - 1), tnk = binomial((n - (n % 2) -2*k)/2, 2*k + (n % 2)) * 2^((n + (n % 2) + 2*k)/2); print1(tnk, ", ");); print(););} \\ Michel Marcus, Sep 26 2014

Formula

T(n,k) = binomial((n - (n mod 2) - 2*k)/2, 2*k + (n mod 2)) * 2^((n + (n mod 2) + 2*k)/2).

Extensions

More terms from Michel Marcus, Sep 26 2014
Previous Showing 11-19 of 19 results.