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 11-20 of 25 results. Next

A385256 Decimal expansion of the volume of a gyroelongated triangular bicupola with unit edge.

Original entry on oeis.org

4, 6, 9, 4, 5, 6, 4, 3, 9, 2, 9, 1, 5, 8, 9, 3, 6, 7, 6, 2, 1, 4, 2, 2, 1, 6, 5, 1, 2, 9, 6, 1, 4, 9, 0, 8, 1, 9, 6, 9, 5, 6, 9, 0, 6, 5, 6, 9, 4, 0, 1, 8, 6, 8, 0, 7, 8, 5, 7, 1, 1, 6, 8, 5, 4, 4, 0, 9, 8, 8, 0, 4, 7, 8, 7, 0, 3, 9, 8, 6, 4, 7, 8, 4, 7, 5, 3, 1, 9, 0
Offset: 1

Views

Author

Paolo Xausa, Jun 24 2025

Keywords

Comments

The gyroelongated triangular bicupola is Johnson solid J_44.

Examples

			4.6945643929158936762142216512961490819695690656940...
		

Crossrefs

Cf. A385257 (surface area).

Programs

  • Mathematica
    First[RealDigits[Sqrt[2]*(5/3 + Sqrt[1 + Sqrt[3]]), 10, 100]] (* or *)
    First[RealDigits[PolyhedronData["J44", "Volume"], 10, 100]]

Formula

Equals sqrt(2)*(5/3 + sqrt(1 + sqrt(3))) = A002193*(5/3 + sqrt(A090388)).
Equals the largest real root of 6561*x^8 - 198288*x^6 + 1506600*x^4 - 7125696*x^2 + 2704.

A094433 a(n) is the left term in M^n * [1 0 0], M = the 3 X 3 matrix [1 -1 0 / -1 3 -2 / 0 -2 2].

Original entry on oeis.org

1, 1, 2, 6, 24, 108, 504, 2376, 11232, 53136, 251424, 1189728, 5629824, 26640576, 126064512, 596543616, 2822874624, 13357986048, 63210668544, 299116094976, 1415432558592, 6697898781696, 31694797338624, 149981391341568, 709719564017664, 3358429036056576
Offset: 0

Views

Author

Gary W. Adamson, May 02 2004

Keywords

Comments

Right term of M^n * [1 0 0] = A094434(n).
a(n)/a(n-1) tends to 3 + sqrt(3) = 4.732050807... (A165663).
A094434(n)/a(n) tends to 1 + sqrt(3) = 2.732050807... (A090388).
M is a "stiffness matrix" with k1 = 1, k2 = 2; in K = [k1 -k1 0 / -k1 (k1 + k2) -k2 / 0 -k2 k2], where K relates to Hooke's Law governing the force on nodes of springs resulting from stretching or compressing the springs (see A094431).
The eigenvalues of M are 3+sqrt(3), 3-sqrt(3) and 0. - Tamas Kalmar-Nagy (integers(AT)kalmarnagy.com), Mar 23 2008
a(n) is the number of permutations of length n+1 avoiding the partially ordered pattern (POP) {1>2, 1>3, 1>4, 5>2, 5>3, 5>4} of length 5. That is, the number of length n+1 permutations having no subsequences of length 5 in which the elements in positions 1 and 5 are larger than the elements in positions 2, 3 and 4. - Sergey Kitaev, Dec 11 2020

Examples

			a(4) = 24 since M^4 * [1 0 0] = [24 -84 60].
G.f. = 1 + x + 2*x^2 + 6*x^3 + 24*x^4 + 108*x^5 + 504*x^6 + 2376*x^7 + ...
		

References

  • Carl D. Meyer, "Matrix Analysis and Applied Linear Algebra", SIAM, 2000, p. 86-87.

Crossrefs

Programs

  • Maple
    a:= n-> (<<1|-1|0>, <-1|3|-2>, <0|-2|2>>^n)[1$2]:
    seq(a(n), n=0..28);  # Alois P. Heinz, Dec 11 2020
  • Mathematica
    Table[(MatrixPower[{{1, -1, 0}, {-1, 3, -2}, {0, -2, 2}}, n].{1, 0, 0})[[1]], {n, 24}] (* Robert G. Wilson v *)
    Table[(3 + Sqrt[3])^n + (3 - Sqrt[3])^n, {n, 0, 20}] // Simplify (* Tamas Kalmar-Nagy (integers(AT)kalmarnagy.com), Mar 23 2008 *)
    Rest@ CoefficientList[Series[x (1 - 4 x)/(1 - 6 x + 6 x^2), {x, 0, 23}], x] (* Michael De Vlieger, May 01 2019 *)
  • Sage
    [lucas_number2(n,6,6)for n in range(-1,23)] # Zerinvary Lajos, Jul 08 2008

Formula

a(n) = (3+sqrt(3))^(n-2) + (3-sqrt(3))^(n-2). - Tamas Kalmar-Nagy (integers(AT)kalmarnagy.com), Mar 23 2008 [Corrected by R. J. Mathar, Mar 28 2010, Jun 02 2010]
G.f.: 1 + x*(1-4*x)/(1-6*x+6*x^2). - R. J. Mathar, Mar 28 2010

Extensions

More terms from Robert G. Wilson v, May 08 2004
a(0)=1 prepended by Alois P. Heinz, Dec 11 2020

A377796 Decimal expansion of the surface area of a truncated icosidodecahedron (great rhombicosidodecahedron) with unit edge length.

Original entry on oeis.org

1, 7, 4, 2, 9, 2, 0, 3, 0, 3, 4, 2, 3, 2, 3, 9, 2, 0, 8, 8, 2, 9, 3, 2, 1, 0, 7, 5, 2, 6, 2, 8, 3, 4, 6, 5, 7, 2, 8, 4, 8, 5, 2, 2, 1, 9, 2, 0, 4, 4, 5, 1, 9, 1, 6, 5, 2, 8, 4, 8, 8, 9, 6, 8, 9, 4, 8, 0, 3, 8, 8, 9, 1, 6, 2, 1, 1, 6, 7, 2, 8, 6, 6, 6, 0, 7, 2, 1, 9, 7
Offset: 3

Views

Author

Paolo Xausa, Nov 07 2024

Keywords

Examples

			174.292030342323920882932107526283465728485221920...
		

Crossrefs

Cf. A377797 (volume), A377798 (circumradius), A377799 (midradius).

Programs

  • Mathematica
    First[RealDigits[30*(1 + Sqrt[3] + Sqrt[5 + Sqrt[20]]), 10, 100]] (* or *)
    First[RealDigits[PolyhedronData["TruncatedIcosidodecahedron", "SurfaceArea"], 10, 100]]

Formula

Equals 30*(1 + sqrt(3) + sqrt(5 + 2*sqrt(5))) = 30*(A090388 + A019970).

A378131 Decimal expansion of sqrt(1 + sqrt(3))*L/(Pi*12^(1/8)), where L is the lemniscate constant (A062539).

Original entry on oeis.org

1, 0, 1, 1, 2, 0, 4, 6, 9, 5, 5, 3, 7, 6, 9, 0, 0, 9, 0, 5, 7, 2, 8, 5, 5, 9, 8, 8, 5, 6, 9, 6, 2, 5, 8, 0, 3, 2, 8, 3, 5, 3, 6, 6, 5, 8, 4, 7, 9, 5, 8, 1, 9, 2, 0, 4, 2, 2, 3, 1, 0, 8, 1, 0, 3, 5, 4, 7, 3, 8, 0, 6, 8, 3, 0, 1, 1, 5, 6, 1, 0, 6, 0, 4, 5, 1, 2, 1, 7, 7
Offset: 1

Views

Author

Paolo Xausa, Nov 18 2024

Keywords

Examples

			1.011204695537690090572855988569625803283536658...
		

Crossrefs

Programs

  • Mathematica
    First[RealDigits[Sqrt[(1 + Sqrt[3])*Pi]/(2^(3/4)*3^(1/8)*Gamma[3/4]^2), 10, 100]] (* or *)
    First[RealDigits[Hypergeometric2F1[1/3, 2/3, 1, (3*Sqrt[3] - 5)/4], 10, 100]]

Formula

Equals sqrt((1 + sqrt(3))*Pi)/(2^(3/4)*3^(1/8)*Gamma(3/4)^2) = sqrt(A090388*A000796)/(2^(3/4)*3^(1/8)*A068465^2).
Equals Sum_{j,k integers} exp(-2*Pi*(j^2 + j*k + k^2)).
Equals 2F1(1/3, 2/3, 1, (3*sqrt(3) - 5)/4), where 2F1 is the ordinary hypergeometric function.

A144982 Decimal expansion of cos(Pi/24) = cos(7.5 degrees).

Original entry on oeis.org

9, 9, 1, 4, 4, 4, 8, 6, 1, 3, 7, 3, 8, 1, 0, 4, 1, 1, 1, 4, 4, 5, 5, 7, 5, 2, 6, 9, 2, 8, 5, 6, 2, 8, 7, 1, 2, 7, 7, 7, 3, 8, 2, 7, 4, 4, 4, 8, 1, 0, 2, 2, 7, 1, 4, 5, 8, 7, 7, 4, 6, 0, 3, 5, 2, 8, 9, 2, 2, 0, 6, 8, 4, 0, 5, 0, 8, 2, 5, 3, 1, 7, 6, 3, 2, 6, 5, 4, 3, 3, 4, 5, 3, 2, 7, 7, 3, 9, 7, 3, 5, 7, 3, 7, 8
Offset: 0

Views

Author

R. J. Mathar, Sep 28 2008

Keywords

Comments

Octic number of denominator 2 and minimal polynomial 256x^8 - 512x^6 + 320x^4 - 64x^2 + 1. - Charles R Greathouse IV, May 13 2019

Examples

			Equals 0.9914448613738104111445575269285628712777382744...
		

Programs

Formula

sqrt(2*sqrt(2)+sqrt(3)+1)/2^(5/4) =sqrt(A010466+A090388)/A011027.
Equals 2F1(9/16,7/16;1/2;3/4) / 2 . - R. J. Mathar, Oct 27 2008
4*this^3 -3*this = A144981. - R. J. Mathar, Aug 29 2025
Equals 2F1(-1/16,1/16;1/2;3/4) = 2F1(-1/12,1/12;1/2;1/2). - R. J. Mathar, Aug 31 2025

A224837 Surface area of Johnson square pyramid (rounded down) with all the edge-lengths equal to n.

Original entry on oeis.org

2, 10, 24, 43, 68, 98, 133, 174, 221, 273, 330, 393, 461, 535, 614, 699, 789, 885, 986, 1092, 1204, 1322, 1445, 1573, 1707, 1846, 1991, 2141, 2297, 2458, 2625, 2797, 2975, 3158, 3346, 3540, 3740, 3945, 4155, 4371, 4592, 4819, 5051, 5289, 5532, 5781, 6035, 6294
Offset: 1

Views

Author

K. D. Bajpai, Sep 18 2013

Keywords

Comments

Johnson square pyramid: a square base with four equilateral triangular-faces. All the edge-lengths are equal.

Examples

			a(3) = 24: Surface area = (1+sqrt(3))*3^2 = 24.588... and floor(24.588...) = 24.
		

Crossrefs

Programs

  • Maple
    a:= n-> floor((1+sqrt(3))*n^2):
    seq(a(n), n=1..48);
  • Mathematica
    Table[Floor[(1+Sqrt[3])*k^2], {k, 500}]
  • PARI
    vector(500, k, floor((1+sqrt(3))*k^2))
    
  • PARI
    a(n)=n^2+sqrtint(3*n^4) \\ Charles R Greathouse IV, Sep 18 2013

Formula

a(n) = floor((1+sqrt(3))*n^2).

A256965 Decimal expansion of sqrt(2) + sqrt(3/2).

Original entry on oeis.org

2, 6, 3, 8, 9, 5, 8, 4, 3, 3, 7, 6, 4, 6, 8, 4, 0, 9, 7, 9, 0, 0, 3, 3, 0, 7, 6, 1, 5, 6, 2, 6, 4, 3, 7, 7, 4, 5, 5, 2, 6, 4, 5, 6, 1, 5, 7, 0, 5, 2, 8, 3, 1, 3, 7, 3, 9, 3, 0, 2, 6, 0, 2, 1, 6, 1, 6, 2, 1, 2, 6, 6, 7, 1, 9, 0, 7, 6, 4, 5, 5, 2, 1, 2, 0, 3, 1, 7, 2, 5, 0, 8, 7, 9, 9
Offset: 1

Views

Author

N. J. A. Sloane, Apr 16 2015

Keywords

Comments

Conjectured minimal length of fence ensuring privacy of a square garden.

Examples

			2.6389584337646840979003307615626437745526456157052831373930...
		

References

  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 8.11, p. 517.

Crossrefs

Cf. A090388.

Programs

  • Magma
    SetDefaultRealField(RealField(100)); Sqrt(2) + Sqrt(3/2); // G. C. Greubel, Aug 19 2018
  • Mathematica
    RealDigits[Sqrt[2] + Sqrt[3/2], 10, 110][[1]] (* Vincenzo Librandi, Aug 21 2016 *)
  • PARI
    sqrt(2)+sqrt(3/2) \\ Michel Marcus, Dec 20 2015
    

A317502 Triangle read by rows: T(0,0) = 1; T(n,k) = 3 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, 3, 9, 27, -2, 81, -12, 243, -54, 729, -216, 4, 2187, -810, 36, 6561, -2916, 216, 19683, -10206, 1080, -8, 59049, -34992, 4860, -96, 177147, -118098, 20412, -720, 531441, -393660, 81648, -4320, 16, 1594323, -1299078, 314928, -22680, 240, 4782969, -4251528, 1180980, -108864, 2160
Offset: 0

Views

Author

Shara Lalo, Aug 02 2018

Keywords

Comments

The numbers in rows of the triangle are along "second layer" skew diagonals pointing top-right in center-justified triangle given in A303901 ((3-2*x)^n) and along "second layer" skew diagonals pointing top-left in center-justified triangle given in A317498 ((-2+3x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (3-2*x)^n and (-2+3x)^n are given in A303941 and A302747 respectively.) The coefficients in the expansion of 1/(1-3x+2x^3) are given by the sequence generated by the row sums. The row sums give A077846. If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 2.7320508075688772... (A090388: 1+sqrt(3)), when n approaches infinity.

Examples

			Triangle begins:
        1;
        3;
        9;
        27,        -2;
        81,       -12;
       243,       -54;
       729,      -216,        4;
      2187,      -810,       36;
      6561,     -2916,      216;
     19683,    -10206,     1080,       -8;
     59049,    -34992,     4860,      -96;
    177147,   -118098,    20412,     -720;
    531441,   -393660,    81648,    -4320,    16;
   1594323,  -1299078,   314928,   -22680,   240;
   4782969,  -4251528,  1180980,  -108864,  2160;
  14348907, -13817466,  4330260,  -489888, 15120,  -32;
  43046721, -44641044, 15588936, -2099520, 90720, -576;
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3, pp. 136, 396, 397.

Crossrefs

Row sums give A077846.
Cf. A090388.

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = 3^(n - 3k) * (-2)^k/((n - 3 k)! k!) * (n - 2 k)!; Table[t[n, k], {n, 0, 15}, {k, 0, Floor[n/3]} ]  // Flatten
    t[0, 0] = 1; t[n_, k_] := t[n, k] = If[n < 0 || k < 0, 0, 3 * t[n - 1, k] - 2 * t[n - 3, k - 1]]; Table[t[n, k], {n, 0, 15}, {k, 0, Floor[n/3]}] // Flatten

Formula

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

A317503 Triangle read by rows: T(0,0) = 1; T(n,k) = -2 T(n-1,k) + 3 * 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, 3, 16, -12, -32, 36, 64, -96, 9, -128, 240, -54, 256, -576, 216, -512, 1344, -720, 27, 1024, -3072, 2160, -216, -2048, 6912, -6048, 1080, 4096, -15360, 16128, -4320, 81, -8192, 33792, -41472, 15120, -810, 16384, -73728, 103680, -48384, 4860, -32768, 159744, -253440, 145152, -22680, 243
Offset: 0

Views

Author

Shara Lalo, Aug 02 2018

Keywords

Comments

The numbers in rows of the triangle are along "second layer" skew diagonals pointing top-left in center-justified triangle given in A303901 ((3-2*x)^n) and along "second layer" skew diagonals pointing top-right in center-justified triangle given in A317498 ((-2+3x)^n), see links. (Note: First layer skew diagonals in center-justified triangles of coefficients in expansions of (3-2*x)^n and (-2+3x)^n are given in A303941 and A302747 respectively.) The coefficients in the expansion of 1/(1 + 2x - 3x^3) are given by the sequence generated by the row sums. The row sums give A317499.

Examples

			Triangle begins:
       1;
      -2;
       4;
      -8,       3;
      16,     -12;
     -32,      36;
      64,     -96,       9;
    -128,     240,     -54;
     256,    -576,     216;
    -512,    1344,    -720,      27;
    1024,   -3072,    2160,    -216;
   -2048,    6912,   -6048,    1080;
    4096,  -15360,   16128,   -4320,     81;
   -8192,   33792,  -41472,   15120,   -810;
   16384,  -73728,  103680,  -48384,   4860;
  -32768,  159744, -253440,  145152, -22680,   243;
   65536, -344064,  608256, -414720,  90720, -2916;
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3, pp. 136, 396, 397.

Crossrefs

Row sums give A317499.
Cf. A090388.

Programs

  • Mathematica
    t[n_, k_] := t[n, k] = (-2)^(n - 3k) * 3^k/((n - 3 k)! k!) * (n - 2 k)!; Table[t[n, k], {n, 0, 15}, {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] + 3 * t[n - 3, k - 1]]; Table[t[n, k], {n, 0, 15}, {k, 0, Floor[n/3]}] // Flatten

Formula

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

A337402 Decimal expansion of the length of third shortest diagonal in a regular 12-gon with unit edge length.

Original entry on oeis.org

3, 3, 4, 6, 0, 6, 5, 2, 1, 4, 9, 5, 1, 2, 3, 1, 6, 2, 2, 3, 0, 1, 1, 7, 5, 1, 2, 3, 6, 6, 7, 4, 9, 2, 8, 1, 3, 8, 3, 7, 4, 8, 1, 5, 5, 3, 3, 9, 3, 7, 5, 7, 1, 7, 3, 9, 8, 1, 3, 6, 5, 8, 9, 0, 6, 1, 1, 5, 7, 8, 9, 0, 6, 4, 2, 1, 8, 1, 8, 0, 7, 1, 5, 4, 5, 5, 1
Offset: 1

Views

Author

Mohammed Yaseen, Aug 26 2020

Keywords

Comments

The distinct diagonal lengths in a regular 12-gon ABC...JKL with unit edge length are
AC = sqrt(2 + sqrt(3)) = sqrt(2)/(-1+sqrt(3)) = A188887
AD = sqrt(4 + 2*sqrt(3)) = 2 /(-1+sqrt(3)) = A090388
AE = sqrt(6 + 3*sqrt(3)) = sqrt(6)/(-1+sqrt(3))
AF = sqrt(7 + 4*sqrt(3)) = (1+sqrt(3))/(-1+sqrt(3)) = A019973
AG = sqrt(8 + 4*sqrt(3)) = 2*sqrt(2)/(-1+sqrt(3)) = A214726

Examples

			3.34606521495123162230117512366749281383748155339375...
		

Crossrefs

Programs

  • Mathematica
    First[RealDigits[Sqrt[6+3Sqrt[3]],10,100]] (* Paolo Xausa, Oct 19 2023 *)
  • PARI
    sqrt(6 + 3*sqrt(3)) \\ Michel Marcus, Aug 26 2020

Formula

Equals sin(Pi/3)/sin(Pi/12) = sqrt(2) + 2*cos(Pi/12) = sqrt(3*cot(Pi/12)).
Equals sqrt(6 + 3*sqrt(3)) = sqrt(6)/(-1+sqrt(3)) = (3+sqrt(3))/sqrt(2).
Equals 3*A145439.
Equals Gamma(1/24)*Gamma(11/24)/(Gamma(5/24)*Gamma(7/24)) [Zucker] - R. J. Mathar, Jun 24 2024
Previous Showing 11-20 of 25 results. Next