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.

A026056 a(n) = (d(n)-r(n))/5, where d = A026054 and r is the periodic sequence with fundamental period (3,3,0,0,4).

Original entry on oeis.org

2, 5, 10, 16, 23, 33, 45, 60, 77, 96, 119, 145, 175, 208, 244, 285, 330, 380, 434, 492, 556, 625, 700, 780, 865, 957, 1055, 1160, 1271, 1388, 1513, 1645, 1785, 1932, 2086, 2249, 2420, 2600, 2788, 2984, 3190, 3405, 3630, 3864, 4107, 4361, 4625, 4900, 5185, 5480, 5787, 6105, 6435, 6776, 7128, 7493
Offset: 3

Views

Author

Clark Kimberling

Keywords

Links

Crossrefs

Cf. A152893, A026054.

Formula

a(n) = (n + 2)*(n + 3)*(n + 13)/30 - 1/5*(2 + (1/2 + 7/10*5^(1/2))*cos(2*n*Pi/5) + ( - 1/10*2^(1/2)*(5 + 5^(1/2))^(1/2))*sin(2*n*Pi/5) + (1/2 - 7/10*5^(1/2))*cos(4*n*Pi/5) + ( - 1/10*2^(1/2)*(5 - 5^(1/2))^(1/2))*sin(4*n*Pi/5)). - Richard Choulet, Dec 14 2008
G.f.: x^3*( 2-x+x^2-x^3 ) / ( (x^4+x^3+x^2+x+1)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-5) - 3*a(n-6) + 3*a(n-7) - a(n-8). - Wesley Ivan Hurt, Jul 29 2022

A026055 a(n) = (d(n)-r(n))/2, where d = A026054 and r is the periodic sequence with fundamental period (1,0,0,0).

Original entry on oeis.org

6, 14, 25, 40, 59, 84, 114, 150, 192, 242, 299, 364, 437, 520, 612, 714, 826, 950, 1085, 1232, 1391, 1564, 1750, 1950, 2164, 2394, 2639, 2900, 3177, 3472, 3784, 4114, 4462, 4830, 5217, 5624, 6051, 6500, 6970, 7462, 7976, 8514, 9075, 9660, 10269, 10904, 11564, 12250, 12962, 13702, 14469, 15264
Offset: 3

Views

Author

Clark Kimberling

Keywords

Links

Programs

  • Mathematica
    LinearRecurrence[{3,-3,1,1,-3,3,-1},{6,14,25,40,59,84,114},60] (* Harvey P. Dale, Mar 27 2013 *)

Formula

a(n) = - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) + (n + 2)*(n + 3)*(n + 13)/12 [From Richard Choulet, Dec 13 2008]
a(n) = (n + 2)*(n + 3)*(n + 13)/12 - 0.125 - 0.125*( - 1)^n - 0.25*cos(n*Pi/2) [From Richard Choulet, Dec 13 2008]
G.f.: x^3*( 6-4*x+x^2+x^3+6*x^5-2*x^6-6*x^4 ) / ( (1+x)*(x^2+1)*(x-1)^4 ). - R. J. Mathar, Jun 22 2013

A094415 Triangle T read by rows: dot product * .

Original entry on oeis.org

1, 4, 5, 10, 13, 13, 20, 26, 28, 26, 35, 45, 50, 50, 45, 56, 71, 80, 83, 80, 71, 84, 105, 119, 126, 126, 119, 105, 120, 148, 168, 180, 184, 180, 168, 148, 165, 201, 228, 246, 255, 255, 246, 228, 201, 220, 265, 300, 325, 340, 345, 340, 325, 300, 265, 286, 341
Offset: 0

Views

Author

Ralf Stephan, May 02 2004

Keywords

Examples

			Triangle begins as:
   1;
   4,  5;
  10, 13, 13;
  20, 26, 28, 26;
  35, 45, 50, 50, 45;
  56, 71, 80, 83, 80, 71;

Links

Crossrefs

Columns 0-6 are A000292, A008778, A026054, A026057, A026060, A026063, A026066.
Half-diagonal is A050410.
Row sums are A000537.
See also A094414, A088003.

Programs

  • GAP
    Flat(List([0..12], n-> List([0..n], k-> (n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6 ))); # G. C. Greubel, Oct 30 2019
  • Magma
    [(n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6: k in [0..n], n in [0..12]]; // G. C. Greubel, Oct 30 2019
  • Maple
    seq(seq( (n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6 , k=0..n), n=0..12); # G. C. Greubel, Oct 30 2019
  • Mathematica
    Table[(n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6, {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Oct 30 2019 *)
  • PARI
    T(n,k) = (n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6;
for(n=0,12, for(k=0,n, print1(T(n,k), ", "))) \\ G. C. Greubel, Oct 30 2019
  • Sage
    [[(n+1)*((n+2)*(n+3) + 3*k*(n-k+1))/6 for k in (0..n)] for n in (0..12)] # G. C. Greubel, Oct 30 2019

Formula

T(n, k) = n*(n^2 + 3*n*(1+k) + 2 - 3*k^2)/6 for n >= 0, 0 <= k <= n.

A060488 Number of 4-block ordered tricoverings of an unlabeled n-set.

Original entry on oeis.org

4, 13, 28, 50, 80, 119, 168, 228, 300, 385, 484, 598, 728, 875, 1040, 1224, 1428, 1653, 1900, 2170, 2464, 2783, 3128, 3500, 3900, 4329, 4788, 5278, 5800, 6355, 6944, 7568, 8228, 8925, 9660, 10434, 11248, 12103, 13000, 13940, 14924, 15953, 17028, 18150, 19320
Offset: 3

Views

Author

Vladeta Jovovic, Mar 20 2001

Keywords

Comments

A covering of a set is a tricovering if every element of the set is covered by exactly three blocks of the covering.
If Y is a 4-subset of an n-set X then, for n>=6, a(n-3) is the number of 3-subsets of X having at most one element in common with Y. - Milan Janjic, Dec 08 2007
Also the number of balls in a triangular pyramid of which all balls located on the edges have been removed such that the remaining pyramid's edges each consist of two adjacent balls. The layers of pyramids of this form start (from the top) 3, 7, 12, 18, 25, 33,... (A055998) with one smaller additional layer 1, 3, 6, 10, 15, 21,... (A000217) at the bottom. Thus, a(n) = A000217(n) + Sum_{k=1..n} A055998(k). Example: a(4) = (3+7+12+18)+10 = 50. - K. G. Stier, Dec 12 2012

Links

Crossrefs

Essentially the same as A026054. - Vladeta Jovovic, Jun 15 2006
Column k=4 of A060492.
Cf. A060091, A060491.
Fourth column (m=3) of (1, 4)-Pascal triangle A095666.

Programs

Formula

a(n) = binomial(n+3, 3) - 6*binomial(n+1, 1) + 8*binomial(n, 0) - 3*binomial(n-1, -1).
G.f.: -y^3*(-4+3*y)/(-1+y)^4.
E.g.f. for ordered k-block tricoverings of an unlabeled n-set is exp(-x+x^2/2+x^3/3*y/(1-y)) * sum(k>=0, 1/(1-y)^binomial(k, 3)*exp(-x^2/2*1/(1-y)^n)*x^k/k! ).
a(n) = (n+9)*binomial(n-1, 2)/3.
a(n) = (n-2)*(n-1)*(n+9)/6. - Zak Seidov, Jun 15 2006
a(3)=4, a(4)=13, a(5)=28, a(6)=50, a(n) = 4*a(n-1)-6*a(n-2)+ 4*a(n-3)- a(n-4). - Harvey P. Dale, Jul 21 2012
Showing 1-4 of 4 results.

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