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 1-6 of 6 results.

A027941 a(n) = Fibonacci(2*n + 1) - 1.

Original entry on oeis.org

0, 1, 4, 12, 33, 88, 232, 609, 1596, 4180, 10945, 28656, 75024, 196417, 514228, 1346268, 3524577, 9227464, 24157816, 63245985, 165580140, 433494436, 1134903169, 2971215072, 7778742048, 20365011073, 53316291172, 139583862444, 365435296161, 956722026040
Offset: 0

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Author

Keywords

Comments

Also T(2n+1,n+1), T given by A027935. Also first row of Inverse Stolarsky array.
Third diagonal of array defined by T(i, 1)=T(1, j)=1, T(i, j)=Max(T(i-1, j)+T(i-1, j-1); T(i-1, j-1)+T(i, j-1)). - Benoit Cloitre, Aug 05 2003
Number of Schroeder paths of length 2(n+1) having exactly one up step starting at an even height (a Schroeder path is a lattice path starting from (0,0), ending at a point on the x-axis, consisting only of steps U=(1,1) (up steps), D=(1,-1) (down steps) and H=(2,0) (level steps) and never going below the x-axis). Schroeder paths are counted by the large Schroeder numbers (A006318). Example: a(1)=4 because among the six Schroeder paths of length 4 only the paths (U)HD, (U)UDD, H(U)D, (U)DH have exactly one U step that starts at an even height (shown between parentheses). - Emeric Deutsch, Dec 19 2004
Also: smallest number not writeable as the sum of fewer than n positive Fibonacci numbers. E.g., a(5)=88 because it is the smallest number that needs at least 5 Fibonacci numbers: 88 = 55 + 21 + 8 + 3 + 1. - Johan Claes, Apr 19 2005 [corrected for offset and clarification by Mike Speciner, Sep 19 2023] In general, a(n) is the sum of n positive Fibonacci numbers as a(n) = Sum_{i=1..n} A000045(2*i). See A001076 when negative Fibonacci numbers can be included in the sum. - Mike Speciner, Sep 24 2023
Except for first term, numbers a(n) that set a new record in the number of Fibonacci numbers needed to sum up to n. Position of records in sequence A007895. - Ralf Stephan, May 15 2005
Successive extremal petal bends beta(n) = a(n-2). See the Ring Lemma of Rodin and Sullivan in K. Stephenson, Introduction to Circle Packing (Cambridge U. P., 2005), pp. 73-74 and 318-321. - David W. Cantrell (DWCantrell(AT)sigmaxi.net)
a(n+1)= AAB^(n)(1), n>=1, with compositions of Wythoff's complementary A(n):=A000201(n) and B(n)=A001950(n) sequences. See the W. Lang link under A135817 for the Wythoff representation of numbers (with A as 1 and B as 0 and the argument 1 omitted). E.g., 4=`110`, 12=`1100`, 33=`11000`, 88=`110000`, ..., in Wythoff code. AA(1)=1=a(1) but for uniqueness reason 1=A(1) in Wythoff code. - N. J. A. Sloane, Jun 29 2008
Start with n. Each n generates a sublist {n-1,n-1,n-2,..,1}. Each element of each sublist also generates a sublist. Add numbers in all terms. For example, 3->{2,2,1} and both 2->{1,1}, so a(3) = 3 + 2 + 2 + 1 + 1 + 1 + 1 + 1 = 12. - Jon Perry, Sep 01 2012
For n>0: smallest number such that the inner product of Zeckendorf binary representation and its reverse equals n: A216176(a(n)) = n, see also A189920. - Reinhard Zumkeller, Mar 10 2013
Also, numbers m such that 5*m*(m+2)+1 is a square. - Bruno Berselli, May 19 2014
Also, number of nonempty submultisets of multisets of weight n that span an initial interval of integers (see 2nd example). - Gus Wiseman, Feb 10 2015
From Robert K. Moniot, Oct 04 2020: (Start)
Including a(-1):=0, consecutive terms (a(n-1),a(n))=(u,v) or (v,u) give all points on the hyperbola u^2-u+v^2-v-4*u*v=0 with both coordinates nonnegative integers. Note that this follows from identifying (1,u+1,v+1) with the Markov triple (1,Fibonacci(2n-1),Fibonacci(2n+1)). See A001519 (comments by Robert G. Wilson, Oct 05 2005, and Wolfdieter Lang, Jan 30 2015).
Let T(n) denote the n-th triangular number. If i, j are any two successive elements of the above sequence then (T(i-1) + T(j-1))/T(i+j-1) = 3/5. (End)

Examples

			a(5) = 88 = 2*33 + 12 + 4 + 1 + 5. a(6) = 232 = 2*88 + 33 + 12 + 4 + 1 + 6. - _Jon Perry_, Sep 01 2012
a(4) = 33 counts all nonempty submultisets of the last row: [1][2][3][4], [11][12][13][14][22][23][24][33][34], [111][112][113][122][123][124][133][134][222][223][233][234], [1111][1112][1122][1123][1222][1223][1233][1234]. - _Gus Wiseman_, Feb 10 2015
		

References

  • A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 12.

Crossrefs

Related to partial sums of Fibonacci(k*n) over n: A000071, A099919, A058038, A138134, A053606; this sequence is the case k=2.
Cf. A212336 for more sequences with g.f. of the type 1/(1 - k*x + k*x^2 - x^3).
Cf. A000225 (sublist connection).
Cf. A258993 (row sums, n > 0), A000967.

Programs

Formula

a(n) = Sum_{i=1..n} binomial(n+i, n-i). - Benoit Cloitre, Oct 15 2002
G.f.: Sum_{k>=1} x^k/(1-x)^(2*k+1). - Benoit Cloitre, Apr 21 2003
a(n) = Sum_{k=1..n} F(2*k), i.e., partial sums of A001906. - Benoit Cloitre, Oct 27 2003
a(n) = Sum_{k=0..n-1} U(k, 3/2) = Sum_{k=0..n-1} S(k, 3), with S(k, 3) = A001906(k+1). - Paul Barry, Nov 14 2003
G.f.: x/((1-x)*(1-3*x+x^2)) = x/(1-4*x+4*x^2-x^3).
a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3) with n>=2, a(-1)=0, a(0)=0, a(1)=1.
a(n) = 3*a(n-1) - a(n-2) + 1 with n>=1, a(-1)=0, a(0)=0.
a(n) = Sum_{k=1..n} F(k)*L(k), where L(k) = Lucas(k) = A000032(k) = F(k-1) + F(k+1). - Alexander Adamchuk, May 18 2007
a(n) = 2*a(n-1) + (Sum_{k=1..n-2} a(k)) + n. - Jon Perry, Sep 01 2012
Sum {n >= 1} 1/a(n) = 3 - phi, where phi = 1/2*(1 + sqrt(5)) is the golden ratio. The ratio of adjacent terms r(n) := a(n)/a(n-1) satisfies the recurrence r(n+1) = (4*r(n) - 1)/(r(n) + 1) for n >= 2. - Peter Bala, Dec 05 2013
a(n) = S(n, 3) - S(n-1, 3) - 1, n >= 0, with Chebyshev's S-polynomials (see A049310), where S(-1, x) = 0. - Wolfdieter Lang, Aug 28 2014
a(n) = -1 + (2^(-1-n)*((3-sqrt(5))^n*(-1+sqrt(5)) + (1+sqrt(5))*(3+sqrt(5))^n)) / sqrt(5). - Colin Barker, Jun 03 2016
E.g.f.: (sqrt(5)*sinh(sqrt(5)*x/2) + 5*cosh(sqrt(5)*x/2))*exp(3*x/2)/5 - exp(x). - Ilya Gutkovskiy, Jun 03 2016
a(n) = Sum_{k=0..n} binomial(n+1,k+1)*Fibonacci(k). - Vladimir Kruchinin, Oct 14 2016
a(n) = Sum_{k=0..n-1} Sum_{i=0..n-1} C(k+i+1,k-i). - Wesley Ivan Hurt, Sep 21 2017
a(n)*a(n-2) = a(n-1)*(a(n-1) - 1) for n>1. - Robert K. Moniot, Aug 23 2020
a(n) = Sum_{k=1..n} C(2*n-k,k). - Wesley Ivan Hurt, Dec 22 2020
a(n) = Sum_{k = 1..2*n+2} (-1)^k*Fibonacci(k). - Peter Bala, Nov 14 2021
a(n) = (2*cosh((1 + 2*n)*arccsch(2)))/sqrt(5) - 1. - Peter Luschny, Nov 21 2021
a(n) = F(n + (n mod 2)) * L(n+1 - (n mod 2)), where L(n) = A000032(n) and F(n) = A000045(n) (Euler and Sadek, 2001). - Amiram Eldar, Jan 13 2022

Extensions

More terms from James Sellers, Sep 08 2000
Paul Barry's Nov 14 2003 formula, recurrences and g.f. corrected for offset 0 and index link for Chebyshev polynomials added by Wolfdieter Lang, Aug 28 2014

A035506 Stolarsky array read by antidiagonals.

Original entry on oeis.org

1, 2, 4, 3, 6, 7, 5, 10, 11, 9, 8, 16, 18, 15, 12, 13, 26, 29, 24, 19, 14, 21, 42, 47, 39, 31, 23, 17, 34, 68, 76, 63, 50, 37, 28, 20, 55, 110, 123, 102, 81, 60, 45, 32, 22, 89, 178, 199, 165, 131, 97, 73, 52, 36, 25, 144, 288, 322, 267, 212, 157, 118, 84, 58, 40, 27, 233, 466, 521, 432, 343, 254, 191, 136, 94, 65, 44, 30
Offset: 0

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Comments

Inverse of sequence A064357 considered as a permutation of the positive integers. - Howard A. Landman, Sep 25 2001
The PARI/GP script gives a general solution for the Stolarsky array in square array form by row, column. Increase the default precision to compute large values in the array. - Randall L Rathbun, Jan 25 2002
The Stolarsky array is the dispersion of the sequence s given by s(n)=(integer nearest n*x), where x=(golden ratio). For a discussion of dispersions, see A191426.
See A098861 for the row in which is a given number. - M. F. Hasler, Nov 05 2014
Named after the American mathematician Kenneth Barry Stolarsky. - Amiram Eldar, Jun 11 2021

Examples

			Top left corner of the array is:
   1    2    3    5    8   13   21   34   55
   4    6   10   16   26   42   68  110  178
   7   11   18   29   47   76  123  119  322
   9   15   24   39   63  102  165  267  432
  12   19   31   50   81  131  212  343  555
  14   23   37   60   97  157  254  411  665
		

References

  • C. Kimberling, "Stolarsky interspersions," Ars Combinatoria 39 (1995) 129-138.

Crossrefs

Cf. A035513 (Wythoff array), A035507 (inverse Stolarsky array), A191426.
Main diagonal gives A035489.

Programs

  • Maple
    A:= proc(n, k) local t, a, b; t:= (1+sqrt(5))/2; a:= floor(n*(t+1)+1 +t/2); b:= round(a*t); (Matrix([[b, a]]). Matrix([[1, 1], [1, 0]])^k) [1, 2] end: seq(seq(A (n, d-n), n=0..d), d=0..10); # Alois P. Heinz, Aug 17 2008
  • Mathematica
    (* program generates the dispersion array T of the complement of increasing sequence f[n] *)
    r = 40; r1 = 12; (* r=# rows of T, r1=# rows to show *)
    c = 40; c1 = 12; (* c=# cols of T, c1=# cols to show *)
    x = GoldenRatio; f[n_] := Floor[n*x + 1/2]
    (* f(n) is complement of column 1 *)
    mex[list_] := NestWhile[#1 + 1 &, 1, Union[list][[#1]] <= #1 &, 1, Length[Union[list]]]
    rows = {NestList[f, 1, c]};
    Do[rows = Append[rows, NestList[f, mex[Flatten[rows]], r]], {r}];
    t[i_, j_] := rows[[i, j]];
    TableForm[Table[t[i, j], {i, 1, 10}, {j, 1, 10}]]
    (* t=Stolarsky array, A035506 *)
    Flatten[Table[t[k, n - k + 1], {n, 1, c1}, {k, 1, n}]]
    (* Stolarsky array as a sequence *)
    (* Program by Peter J. C. Moses, Jun 01 2011 *)
    (* Second program: *)
    A[n_, k_] := Module[{t, a, b}, t = (1+Sqrt[5])/2; a = Floor[n*(t+1)+1+t/2]; b = Round[a*t]; ({b, a}.MatrixPower[{{1, 1}, {1, 0}}, k])[[2]]];
    Table[A[n, d-n], {d, 0, 11}, {n, 0, d}] // Flatten (* Jean-François Alcover, Mar 22 2023, after Alois P. Heinz *)
  • PARI
    {Stolarsky(r,c)= tau=(1+sqrt(5))/2; a=floor(r*(1+tau)-tau/2); b=round(a*tau); if(c==1,a, if(c==2,b, for(i=1,c-2,d=a+b; a=b; b=d; ); d))} \\ Randall L Rathbun, Jan 25 2002

Formula

T(1,k) = 2*T(0,k+1); T(3,k) = 3*T(0,k+2). - M. F. Hasler, Nov 05 2014

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Sep 27 2000
Extended (terms, Mathematica, example) by Clark Kimberling, Jun 03 2011
Example corrected by M. F. Hasler, Nov 05 2014

A035508 a(n) = Fibonacci(2*n+2) - 1.

Original entry on oeis.org

0, 2, 7, 20, 54, 143, 376, 986, 2583, 6764, 17710, 46367, 121392, 317810, 832039, 2178308, 5702886, 14930351, 39088168, 102334154, 267914295, 701408732, 1836311902, 4807526975, 12586269024, 32951280098, 86267571271, 225851433716
Offset: 0

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Comments

Except for 0, numbers whose dual Zeckendorf representation (A104326) has the same number of 0's as 1's. - Amiram Eldar, Mar 22 2021

Crossrefs

With different offset: 2nd row of Inverse Stolarsky array A035507.
Cf. A001906, A104326, A112844, A152891 (partial sums).

Programs

  • Magma
    [Fibonacci(2*n+2)-1: n in [0..30]]; // Vincenzo Librandi, Apr 18 2011
    
  • Maple
    g:=z/(1-3*z+z^2): gser:=series(g, z=0, 43): seq(abs(coeff(gser, z, n)-1), n=1..26); # Zerinvary Lajos, Mar 22 2009
    with(combinat):seq(fibonacci(4*n+2) mod fibonacci(2*n+2),n=0..25);
  • Mathematica
    Fibonacci[2*Range[0, 5!]] - 1 (* Vladimir Joseph Stephan Orlovsky, May 18 2010 *)
    LinearRecurrence[{4,-4,1},{0,2,7},40] (* Harvey P. Dale, Jan 15 2025 *)
  • Maxima
    makelist(fib(2*n+2)-1,n,0,30); /* Martin Ettl, Oct 21 2012 */
  • MuPAD
    numlib::fibonacci(2*n)-1 $ n = 1..38; // Zerinvary Lajos, May 08 2008
    
  • Sage
    [lucas_number1(n, 3, 1)-1 for n in range(1, 27)] # Zerinvary Lajos, Dec 07 2009
    

Formula

a(n) = A001906(n) - 1.
G.f.: x*(2 - x)/((1 - x)*(1 - 3*x + x^2)). a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3). - R. J. Mathar, Dec 15 2008; adapted to the offset by Bruno Berselli, Apr 19 2011
a(n) = Fibonacci(4*n+2) mod Fibonacci(2*n+2). - Gary Detlefs, Nov 22 2010
a(n+1) = Sum_{k=0..n} Fibonacci(2*k+3). - Gary Detlefs, Dec 24 2010
a(n) = Sum_{i=1..n} A112844(i). - R. J. Mathar, Apr 19 2011
a(n) = floor(Fibonacci(2*n+2) - Fibonacci(n+1)^2/Fibonacci(2*n+2)). - Gary Detlefs, Dec 21 2012
From Peter Bala, Nov 14 2021: (Start)
a(n) = Fibonacci(2*n+4)*(Fibonacci(2*n+1) - 1)/(Fibonacci(2*n+3) - 1).
a(n)= -2 + Sum_{k = 1..2*n+3} (-1)^(k+1)*Fibonacci(k). (End)

A035509 Main diagonal of Inverse Stolarsky array.

Original entry on oeis.org

1, 7, 25, 101, 321, 1075, 3426, 9958, 30253, 92735, 253731, 739303, 2056915, 5899304, 17108660, 46137324, 130016549, 370248450, 993480845, 2766546762, 7510827752, 20798505510, 58123818148, 155141346542, 426530329383
Offset: 0

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Keywords

Crossrefs

Cf. A035507.

Programs

  • Maple
    with(combinat, fibonacci): gold:=(1+sqrt(5))/2: c1:=n->piecewise(n<>1,round((n-1)*gold),1): c2:=n->c1(n)+floor((2*c1(n)+1)*gold/2)+1: inv_stol:=(n,k)->fibonacci(2*k-3)-1-c1(n)*fibonacci(2*k-4)+c2(n)*fibonacci(2*k-2): seq(inv_stol(n,n),n=1..30); inv_stol2:=(n,k)->(1+c1(n))*fibonacci(2*k-3)+(1+floor((2*c1(n)+1)*gold/2))*fibonacci(2*k-2)-1: seq(inv_stol2(n,n),n=1..30); inv_stol3:=proc(n,k) options remember: if k=1 then RETURN(c1(n)) elif k=2 then RETURN(c2(n)) else RETURN(3*inv_stol3(n,k-1)-inv_stol3(n,k-2)+1) fi: end: : seq(inv_stol3(n,n),n=1..30); (Ronaldo)

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005

A035510 2nd column of Inverse Stolarsky array.

Original entry on oeis.org

4, 7, 9, 14, 17, 22, 27, 30, 35, 41, 43, 48, 51, 56, 62, 64, 69, 75, 77, 82, 85, 90, 96, 98, 103, 106, 111, 117, 119, 124, 130, 132, 137, 140, 145, 151, 153, 158, 161, 166, 171, 174, 179, 185, 187, 192, 195, 200, 206, 208, 213, 219, 221, 226, 229, 234, 240, 242
Offset: 0

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Author

Keywords

Crossrefs

Cf. A035507.

Programs

  • Maple
    tau:=(1+sqrt(5))/2: 4,seq(round(n*tau)+1+floor((round(n*tau)+1/2)*tau),n=1..100); # C. Ronaldo

Formula

a(n) = round(n*tau) + 1 + floor((round(n*tau) + 1/2)*tau) for n > 0 with a(0)=4. - C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005

A035511 3rd column of Inverse Stolarsky array.

Original entry on oeis.org

12, 20, 25, 38, 46, 59, 72, 80, 93, 109, 114, 127, 135, 148, 164, 169, 182, 198, 203, 216, 224, 237, 253, 258, 271, 279, 292, 308, 313, 326, 342, 347, 360, 368, 381, 397, 402, 415, 423, 436, 449, 457, 470, 486, 491, 504, 512, 525, 541, 546, 559, 575, 580, 593
Offset: 0

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Author

Keywords

Crossrefs

Cf. A035507.

Programs

  • Maple
    tau:=(1+sqrt(5))/2: 12,seq((2*round(n*tau)+1)+3*floor((2*round(n*tau)+1)*tau/2)+3,n=1..69); # C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005

Formula

a(n) = (2*round(n*tau)+1) + 3*(floor((round(n*tau) + 1/2)*tau)+1) for n > 0 and a(0)=12, tau = (1+sqrt(5))/2. - C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 01 2005
Showing 1-6 of 6 results.