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.

A160156 Partial sums of A007583.

Original entry on oeis.org

1, 4, 15, 58, 229, 912, 3643, 14566, 58257, 233020, 932071, 3728274, 14913085, 59652328, 238609299, 954437182, 3817748713, 15270994836, 61083979327, 244335917290, 977343669141, 3909374676544, 15637498706155, 62549994824598
Offset: 0

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Author

Omar E. Pol, May 27 2009

Keywords

Comments

This sequence is one of 104 sequences mentioned in the Lang's paper; see page 4. - Omar E. Pol, Jun 13 2012
Also 1 plus the total number of toothpicks of the first n toothpick structures of A139250 in which the number of exposed toothpicks that are orthogonals to the initial toothpick is equal to 4. - Omar E. Pol, Jun 16 2012
This is the sequence A(1,4;5,-4;-1,n) of the family of sequences [a,b:c,d:k] considered by Gary Detlefs, and treated as A(a,b;c,d;k) in the W. Lang link given below. - Wolfdieter Lang, Nov 16 2013

Examples

			G.f. = 1 + 4*x + 15*x^2 + 58*x^3 + 229*x^4 + 912*x^5 + 3643*x^6 + ... - _Michael Somos_, Oct 16 2020
		

Crossrefs

Programs

  • Maple
    a := proc (n) options operator, arrow: (1/3)*n+1/9+(1/9)*2^(2*n+3) end proc: seq(a(n), n = 0 .. 25); # Emeric Deutsch, Jun 20 2009
  • Mathematica
    LinearRecurrence[{6,-9,4},{1,4,15},30] (* Harvey P. Dale, Oct 04 2018 *)
  • PARI
    {a(n) = (2^(2*n + 3) + 3*n + 1)/9}; /* Michael Somos, Oct 16 2020 */

Formula

a(n) = (3n + 1 + 2^(2n+3))/9. - Emeric Deutsch, Jun 20 2009
G.f.: ( -1+2*x ) / ( (-1+4*x)*(x-1)^2 ). - R. J. Mathar, Jun 28 2012
From Wolfdieter Lang, Nov 16 2013: (Start)
a(n) = 6*a(n-1) - 9*a(n-2) + 4*a(n-3), n >= 2, a(-1)=0, a(0)=1, a(1)=4.
a(n) = 5*a(n-1) - 4*a(n-2) -1, n >= 2, a(0)=1, a(1)=4. (End)
a(n) = A034299(2*n). - Michael Somos, Oct 16 2020

Extensions

More terms from Emeric Deutsch, Jun 20 2009

A103196 a(n) = (1/9)(2^(n+3)-(-1)^n(3n-1)).

Original entry on oeis.org

1, 2, 3, 8, 13, 30, 55, 116, 225, 458, 907, 1824, 3637, 7286, 14559, 29132, 58249, 116514, 233011, 466040, 932061, 1864142, 3728263, 7456548, 14913073, 29826170, 59652315, 119304656, 238609285, 477218598, 954437167
Offset: 0

Views

Author

Creighton Dement, Mar 18 2005

Keywords

Comments

A floretion-generated sequence relating to the Jacobsthal sequence A001045 as well as to A095342 (Number of elements in n-th string generated by a Kolakoski(5,1) rule starting with a(1)=1). (a(n)) may be seen as the result of a certain transform of the natural numbers (see program code).
Floretion Algebra Multiplication Program, FAMP Code: 4jesleftforseq[A*B] with A = + 'i + 'j + i' + j' + 'ii' + 'jj' + 'ij' + 'ji' + e and B = - .25'i + .25'j + .25'k + .25i' - .25j' + .25k' - .25'ii' + .25'jj' + .25'kk' + .25'ij' + .25'ik' + .25'ji' + .25'jk' - .25'ki' - .25'kj' - .25e; 1vesforseq[A*B](n) = n, ForType: 1A.

Crossrefs

Programs

  • Mathematica
    Table[(2^(n+3)-(-1)^n (3n-1))/9,{n,0,30}] (* or *) LinearRecurrence[ {0,3,2},{1,2,3},40] (* Harvey P. Dale, Jul 09 2018 *)

Formula

G.f. (2x+1)/((1-2x)(x+1)^2); Superseeker results: a(n) + a(n+1) = A001045(n+3); a(n+1) - a(n) = A095342(n+1); a(n+2) - a(n+1) - a(n) = A053088(n+1) = A034299(n+1) - A034299(n); a(n) + 2a(n+1) + a(n+2) = 2^(n+3); a(n+2) - 2a(n+1) + a(n) = A053088(n+1) - A053088(n); a(n+2) - a(n) = A001045(n+4) - A001045(n+3) = A052953(n+3) - A052953(n+2) = A026644(n+2) - A026644(n+1);
a(n)=sum{k=0..n+2, (-1)^(n-k)*C(n+2, k)phi(phi(3^k))}; a(n)=sum{k=0..n+2, (-1)^(n-k)*C(n+2, k)(2*3^k/9+C(1, k)/3+4*C(0, k)/9)}; a(n)=sum{k=0..n+2, J(n-k+3)((-1)^(k+1)-2C(1, k)+4C(0, k))} where J(n)=A001045(n); a(n)=A113954(n+2). - Paul Barry, Nov 09 2005

A116914 Number of UUDD's, where U=(1,1) and D=(1,-1), in all hill-free Dyck paths of semilength n (a hill in a Dyck path is a peak at level 1).

Original entry on oeis.org

1, 1, 5, 16, 58, 211, 781, 2920, 11006, 41746, 159154, 609324, 2341060, 9021559, 34855741, 134972368, 523689718, 2035462990, 7923732118, 30889008112, 120566373676, 471134916286, 1842964183570, 7216096752496, 28279240308268, 110913181145716, 435333520075796, 1709861650762900
Offset: 2

Views

Author

Emeric Deutsch, May 08 2006

Keywords

Comments

Catalan transform of A034299. - R. J. Mathar, Jun 29 2009

Examples

			a(4)=5 because in the 6 (=A000957(5)) hill-free Dyck paths of semilength 4, namely UU(UUDD)DD, UUUDUDDD, UUD(UUDD)D, UUDUDUDD, U(UUDD)UDD and (UUDD)(UUDD) (U=(1,1), D=(1,-1)) we have altogether 5 UUDD's (shown between parentheses).
		

Crossrefs

Cf. A105640.

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 40); Coefficients(R!( x*(1 + 5*x-(1-x)*Sqrt(1-4*x))/(2*(2+x)^2*Sqrt(1-4*x)) )); // G. C. Greubel, May 08 2019
    
  • Maple
    G:=z*(1+5*z-(1-z)*sqrt(1-4*z))/2/(2+z)^2/sqrt(1-4*z): Gser:=series(G,z=0,31): seq(coeff(Gser,z^n),n=2..28);
  • Mathematica
    Rest[Rest[CoefficientList[Series[x*(1+5*x-(1-x)*Sqrt[1-4*x])/2/(2+x)^2/Sqrt[1-4*x], {x, 0, 40}], x]]] (* Vaclav Kotesovec, Mar 20 2014 *)
  • PARI
    my(x='x+O('x^40)); Vec(x*(1+5*x-(1-x)*sqrt(1-4*x))/(2*(2+x)^2 *sqrt(1-4*x))) \\ G. C. Greubel, Feb 08 2017
    
  • Sage
    a=(x*(1+5*x-(1-x)*sqrt(1-4*x))/(2*(2+x)^2*sqrt(1-4*x))).series(x, 40).coefficients(x, sparse=False); a[2:] # G. C. Greubel, May 08 2019

Formula

a(n) = Sum_{k=0..floor(n/2)} k*A105640(n,k).
G.f.: x*(1 + 5*x - (1-x)*sqrt(1-4*x))/(2*(2+x)^2*sqrt(1-4*x)).
a(n+2) = A126258(2*n,n). - Philippe Deléham, Mar 13 2007
a(n) ~ 2^(2*n-1)/(9*sqrt(Pi*n)). - Vaclav Kotesovec, Mar 20 2014
D-finite with recurrence +2*(-n+1)*a(n) +3*(-n+6)*a(n-1) +3*(13*n-44)*a(n-2) +10*(2*n-5)*a(n-3)=0. - R. J. Mathar, Jul 26 2022

A126258 Triangle generated by Pascal's rule with left diagonal = [1,0,2,0,3,0,4,...] (A000027 with interpolated zeros) and right diagonal = [1,1,1,1,1,...].

Original entry on oeis.org

1, 0, 1, 2, 1, 1, 0, 3, 2, 1, 3, 3, 5, 3, 1, 0, 6, 8, 8, 4, 1, 4, 6, 14, 16, 12, 5, 1, 0, 10, 20, 30, 28, 17, 6, 1, 5, 10, 30, 50, 58, 45, 23, 7, 1, 0, 15, 40, 80, 108, 103, 68, 30, 8, 1, 6, 15, 55, 120, 188, 211, 171, 98, 38, 9, 1, 0, 21, 70, 175, 308, 399, 382, 269, 136, 47, 10, 1
Offset: 0

Views

Author

Philippe Deléham, Mar 08 2007

Keywords

Examples

			Triangle begins:
  1;
  0, 1;
  2, 1, 1;
  0, 3, 2, 1;
  3, 3, 5, 3, 1;
  0, 6, 8, 8, 4, 1;
  4, 6, 14, 16, 12, 5, 1;
  0, 10, 20, 30, 28, 17, 6, 1;
		

Crossrefs

Formula

T(2*n,n) = A116914(n).
Sum_{k=0..n} T(n,k) = A034299(n).

Extensions

More terms from Jason Yuen, Sep 19 2024
Showing 1-4 of 4 results.