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.

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A080333 Partial sums of A080278.

Original entry on oeis.org

1, 2, 6, 7, 8, 12, 13, 14, 27, 28, 29, 33, 34, 35, 39, 40, 41, 54, 55, 56, 60, 61, 62, 66, 67, 68, 108, 109, 110, 114, 115, 116, 120, 121, 122, 135, 136, 137, 141, 142, 143, 147, 148, 149, 162, 163, 164, 168, 169, 170, 174, 175, 176, 216, 217, 218, 222, 223, 224, 228, 229
Offset: 1

Views

Author

N. J. A. Sloane, Mar 19 2003

Keywords

Crossrefs

Programs

  • PARI
    a(n) = fromdigits(Vec(Pol(digits(3*n,3))'),3); \\ Kevin Ryde, Apr 29 2021

Formula

a(n) = Sum_{k=0..log_3(n)} 3^k*floor(n/3^k).
a(3^k) = (k+1)*3^k.
a(n) is conjectured to be asymptotic to n*log(n)/log(3). - Klaus Brockhaus, Mar 23 2003 [This follows from the asymptotics of A333979. - Pontus von Brömssen, Sep 06 2020]
a(n) = n + 3*a(floor(n/3)), a(0)=0. - Vladeta Jovovic, Aug 06 2003
G.f.: (1/(1 - x))*Sum_{k>=0} 3^k*x^(3^k)/(1 - x^(3^k)). - Ilya Gutkovskiy, Mar 15 2018
a(n) = A333979(3*n,3). - Pontus von Brömssen, Sep 06 2020

A118822 Numerators of the convergents of the 2-adic continued fraction of zero given by A118821.

Original entry on oeis.org

2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1, -2, 1, 0, 1, 2, -1, 0, -1
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118822(k)/A118823(k) are:
  at k = 4*n: -1/A080277(n);
  at k = 4*n+1: -2/(2*A080277(n)-1);
  at k = 4*n+2: -1/(A080277(n)-1);
  at k = 4*n-1: 0/(-1)^n.
Convergents begin:
  2/1, -1/-1, 0/-1, -1/1, -2/1, 1/0, 0/1, 1/-4,
  2/-7, -1/3, 0/-1, -1/5, -2/9, 1/-4, 0/1, 1/-12,
  2/-23, -1/11, 0/-1, -1/13, -2/25, 1/-12, 0/1, 1/-16,
  2/-31, -1/15, 0/-1, -1/17, -2/33, 1/-16, 0/1, 1/-32, ...
		

Crossrefs

Cf. A118821 (partial quotients), A118823 (denominators).

Programs

  • Maple
    A118822:=n->sqrt((n+1)^2 mod 8)*(-1)^floor((n+2)/4); seq(A118822(n), n=1..100); # Wesley Ivan Hurt, Jan 01 2014
  • Mathematica
    Table[Sqrt[Mod[(n+1)^2, 8]](-1)^Floor[(n+2)/4], {n, 100}] (* Wesley Ivan Hurt, Jan 01 2014 *)
  • PARI
    {a(n)=local(p=+2,q=-1,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[1,1]}
    for(n=0,80,print1(a(n),", "))
    
  • PARI
    {a(n) = [2,-1,0,-1,-2,1,0,1][(n-1)%8+1];} \\ Joerg Arndt, Jan 02 2014

Formula

Period 8 sequence: [2,-1,0,-1,-2,1,0,1].
G.f.: -x*(x-1)*(x^2+x+2) / ( 1+x^4 ).
a(n) = sqrt((n+1)^2 mod 8)(-1)^floor((n+2)/4). - Wesley Ivan Hurt, Jan 01 2014

A118825 Numerators of the convergents of the 2-adic continued fraction of zero given by A118824.

Original entry on oeis.org

-2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1, 0, 1, -2, -1, 0, -1, 2, 1
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118825(k)/A118826(k) are:
  at k = 4*n: 1/A080277(n);
  at k = 4*n+1: 2/(2*A080277(n)-1);
  at k = 4*n+2: 1/(A080277(n)-1);
  at k = 4*n-1: 0/(-1)^n.
Convergents begin:
  -2/1, -1/1, 0/-1, -1/-1, 2/1, 1/0, 0/1, 1/4,
  -2/-7, -1/-3, 0/-1, -1/-5, 2/9, 1/4, 0/1, 1/12,
  -2/-23, -1/-11, 0/-1, -1/-13, 2/25, 1/12, 0/1, 1/16,
  -2/-31, -1/-15, 0/-1, -1/-17, 2/33, 1/16, 0/1, 1/32, ...
		

Crossrefs

Cf. A118824 (partial quotients), A118826 (denominators), A118822, A230075 (start with a(5)).

Programs

  • Maple
    A118825:=n->sqrt((n+1)^2 mod 8))*(-1)^floor((n+3)/4); seq(A118825(n), n=1..100); # Wesley Ivan Hurt, Jan 04 2014
  • Mathematica
    Table[Sqrt[Mod[(n+1)^2, 8]](-1)^Floor[(n+3)/4], {n, 100}] (* Wesley Ivan Hurt, Jan 04 2014 *)
    PadRight[{},120,{-2,-1,0,-1,2,1,0,1}] (* Harvey P. Dale, May 26 2020 *)
  • PARI
    {a(n)=local(p=-2,q=+1,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[1,1]}

Formula

Period 8 sequence: [ -2,-1,0,-1,2,1,0,1].
G.f.: -x*(1+x)*(x^2-x+2) / ( 1+x^4 ).
a(n) = sqrt((n+1)^2 mod 8)*(-1)^floor((n+3)/4). - Wesley Ivan Hurt, Jan 04 2014

A118831 Numerators of the convergents of the 2-adic continued fraction of zero given by A118830.

Original entry on oeis.org

-1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0, -1, 1, 1, 0, 1, -1, -1, 0
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118831(k)/A118832(k) are:
at k = 4*n: 1/(2*A080277(n));
at k = 4*n+1: 1/(2*A080277(n)-1);
at k = 4*n+2: 1/(2*A080277(n)-2);
at k = 4*n-1: 0.
Convergents begin:
-1/1, -1/2, 0/-1, -1/-2, 1/1, 1/0, 0/1, 1/8,
-1/-7, -1/-6, 0/-1, -1/-10, 1/9, 1/8, 0/1, 1/24,
-1/-23, -1/-22, 0/-1, -1/-26, 1/25, 1/24, 0/1, 1/32,
-1/-31, -1/-30, 0/-1, -1/-34, 1/33, 1/32, 0/1, 1/64, ...
		

Crossrefs

Cf. A118830 (partial quotients), A118832 (denominators).

Programs

  • PARI
    {a(n)=local(p=-1,q=+2,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[1,1]}

Formula

Period 8 sequence: [ -1,-1,0,-1,1,1,0,1].
G.f.: -x*(1+x+x^3)/(1+x^4). [corrected by R. J. Mathar, Jul 22 2009]
a(n) = -a(n-4). - R. J. Mathar, Jul 22 2009

A240400 Numbers n having a partition into distinct parts of form 3^k-2^k.

Original entry on oeis.org

0, 1, 5, 6, 19, 20, 24, 25, 65, 66, 70, 71, 84, 85, 89, 90, 211, 212, 216, 217, 230, 231, 235, 236, 276, 277, 281, 282, 295, 296, 300, 301, 665, 666, 670, 671, 684, 685, 689, 690, 730, 731, 735, 736, 749, 750, 754, 755, 876, 877, 881, 882, 895, 896, 900, 901
Offset: 1

Views

Author

Jon Perry, Apr 04 2014

Keywords

Comments

Numbers n such that there are partitions into distinct parts from A001047. - Joerg Arndt, Apr 06 2014
Based on casting binary numbers as ternary numbers. - Jon Perry, Apr 12 2014

Examples

			25 = 19 + 5 + 1 so 25 is in the sequence.
		

Crossrefs

Cf. A241783 (complement).

Programs

  • Haskell
    a240400 n = a240400_list !! (n-1)
    a240400_list = filter ((> 0) . a241759) [0..]
    -- Reinhard Zumkeller, Apr 28 2014
    
  • JavaScript
    function trimArray(arr) {
    var c, i, j;
    c = new Array();
    for (j = 0; j < arr.length; j++) c[j] = arr[j];
    c.sort(function(a, b) {return a - b;});
    i = -1;
    while(i++ < c.length - 1)
    if (c[i] == c[i + 1]) c.splice(i--, 1);
    return c;
    }
    a = new Array();
    for (i = 0; i < 10; i++)
    a[i] = Math.pow(3, i) - Math.pow(2, i);
    b = new Array();
    bc = 0;
    for (j = 0; j < 130; j++) {
    c = 0;
    s = j.toString(2);
    sl = s.length;
    for (k = 0; k < sl; k++) if (s.charAt(k) == 1) c += a[k];
    b[bc++] = c;
    }
    b = trimArray(b);
    document.write(b);
    
  • Mathematica
    max = 1000; nmax = FindRoot[3^n - 2^n == max, {n, 1}][[1, 2]] // Ceiling; partitions = Select[Table[{3^n - 2^n}, {n, 1, nmax}], (First[#] <= max)&] //. {a___, b_List, c___, d_List, e___} /; Total[b] + Total[d] <= max && FreeQ[p = {a, b, c, d, e}, (j = Join[b, d] // Sort)] && j == Union[j] :> Union[Append[p, j]]; Join[{0}, Total /@ partitions // Sort] (* Jean-François Alcover, Apr 16 2014 *)
  • PARI
    a(n)=if(n<2,n%2,n+3*a(floor(n/2)))

Formula

A241759(a(n)) > 0. - Reinhard Zumkeller, Apr 28 2014
Recursive formula: For n >= 1, a(1)=1 then a(n) = n + 3*a(floor(n/2)). Sum: a(n) = Sum_{k=0..floor(log_2(n))} 3^k*floor(n/2^k). - Benoit Cloitre, Apr 06 2019

A333979 Array read by antidiagonals, n >= 0, k >= 2: T(n,k) is the "digital derivative" of n in base k; if the base k representation of n is Sum_{j>=0} d_j*k^j, then T(n,k) = Sum_{j>=1} d_j*j*k^(j-1).

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 4, 0, 0, 0, 0, 1, 4, 0, 0, 0, 0, 1, 1, 5, 0, 0, 0, 0, 0, 1, 2, 5, 0, 0, 0, 0, 0, 1, 1, 2, 12, 0, 0, 0, 0, 0, 0, 1, 1, 2, 12, 0, 0, 0, 0, 0, 0, 1, 1, 2, 6, 13, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 6, 13
Offset: 0

Views

Author

Pontus von Brömssen, Sep 04 2020

Keywords

Examples

			Array begins:
  n\k|  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16
  ---|---------------------------------------------
   0 |  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
   1 |  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
   2 |  1  0  0  0  0  0  0  0  0  0  0  0  0  0  0
   3 |  1  1  0  0  0  0  0  0  0  0  0  0  0  0  0
   4 |  4  1  1  0  0  0  0  0  0  0  0  0  0  0  0
   5 |  4  1  1  1  0  0  0  0  0  0  0  0  0  0  0
   6 |  5  2  1  1  1  0  0  0  0  0  0  0  0  0  0
   7 |  5  2  1  1  1  1  0  0  0  0  0  0  0  0  0
   8 | 12  2  2  1  1  1  1  0  0  0  0  0  0  0  0
   9 | 12  6  2  1  1  1  1  1  0  0  0  0  0  0  0
  10 | 13  6  2  2  1  1  1  1  1  0  0  0  0  0  0
  11 | 13  6  2  2  1  1  1  1  1  1  0  0  0  0  0
  12 | 16  7  3  2  2  1  1  1  1  1  1  0  0  0  0
  13 | 16  7  3  2  2  1  1  1  1  1  1  1  0  0  0
  14 | 17  7  3  2  2  2  1  1  1  1  1  1  1  0  0
  15 | 17  8  3  3  2  2  1  1  1  1  1  1  1  1  0
  16 | 32  8  8  3  2  2  2  1  1  1  1  1  1  1  1
64 = 2*3^3 + 1*3^2 + 0*3^1 + 1*3^0, so T(64,3) = 2*3*3^2 + 1*2*3^1 + 0*1*3^0 = 60. Alternatively, using the formula T(n,k) = floor(n/k) + k*T(floor(n/k),k), we get T(64,3) = 21 + 3*T(21,3) = 21 + 3*(7 + 3*T(7,3)) = 42 + 9*(2 + 3*T(2,3)) = 60.
		

Crossrefs

Cf. A136013 (column k=2), A080277 (every second term of column k=2), A080333 (every third term of column k=3).

Programs

  • Python
    import sympy
    def A333979(n,k):
      d=sympy.ntheory.factor_.digits(n,k)
      return sum(j*d[-j-1]*k**(j-1) for j in range(1,len(d)-1))
    
  • Python
    # Second program (faster)
    def A333979(n,k):
      return n//k+k*A333979(n//k,k) if n>=k else 0

Formula

T(n,k) = floor(n/k) + k*T(floor(n/k),k). Proof: With n = Sum_{j>=0} d_j*k^j we have floor(n/k) + k*T(floor(n/k),k) = Sum_{j>=1} (d_j*k^(j-1) + k*d_j*(j-1)*k^(j-2)) = Sum_{j>=1} d_j*j*k^(j-1) = T(n,k).
T(n,k) = T(n-1,k) + A055129(A286561(n,k),k). Proof: Let n = Sum_{j>=0} d_j*k^j and pick v so that d_j = 0 for j < v and d_v > 0 (so v = A286561(n,k)). Then n - 1 = sum_{j>=0} e_j*k^j, where e_j = k - 1 for j < v, e_v = d_v - 1, and e_j = d_j for j > v. We get T(n,k) - T(n-1,k) = Sum_{j>=1} j*(d_j-e_j)*k^(j-1) = v*k^(v-1) - (k-1)*Sum_{1<=jA055129(A286561(n,k),k).
For fixed k, T(n,k) ~ n*log(n)/(k*log(k)). (The proof for k = 2 by Bannister et al. (p. 182) can be adapted to general k.)
T(n,k) = Sum_{j>=0} k^j*floor(n/k**(j+1)).

A118823 Denominators of the convergents of the 2-adic continued fraction of zero given by A118821.

Original entry on oeis.org

1, -1, -1, 1, 1, 0, 1, -4, -7, 3, -1, 5, 9, -4, 1, -12, -23, 11, -1, 13, 25, -12, 1, -16, -31, 15, -1, 17, 33, -16, 1, -32, -63, 31, -1, 33, 65, -32, 1, -36, -71, 35, -1, 37, 73, -36, 1, -44, -87, 43, -1, 45, 89, -44, 1, -48, -95, 47, -1, 49, 97, -48, 1, -80, -159, 79, -1, 81, 161, -80, 1, -84, -167, 83, -1, 85, 169, -84, 1, -92
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118822(k)/A118823(k) are:
at k = 4*n: -1/A080277(n);
at k = 4*n+1: -2/(2*A080277(n)-1);
at k = 4*n+2: -1/(A080277(n)-1);
at k = 4*n-1: 0/(-1)^n.
Convergents begin:
2/1, -1/-1, 0/-1, -1/1, -2/1, 1/0, 0/1, 1/-4,
2/-7, -1/3, 0/-1, -1/5, -2/9, 1/-4, 0/1, 1/-12,
2/-23, -1/11, 0/-1, -1/13, -2/25, 1/-12, 0/1, 1/-16,
2/-31, -1/15, 0/-1, -1/17, -2/33, 1/-16, 0/1, 1/-32, ...
		

Crossrefs

Cf. A080277; A118821 (partial quotients), A118822 (numerators).

Programs

  • PARI
    {a(n)=local(p=+2,q=-1,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[2,1]}

Formula

a(4*n) = -(-1)^n*A080277(n); a(4*n+1) = -(-1)^n*(2*A080277(n)-1); a(4*n+2) = (-1)^n*(A080277(n)-1); a(4*n-1) = (-1)^n.

A118826 Denominators of the convergents of the 2-adic continued fraction of zero given by A118824.

Original entry on oeis.org

1, 1, -1, -1, 1, 0, 1, 4, -7, -3, -1, -5, 9, 4, 1, 12, -23, -11, -1, -13, 25, 12, 1, 16, -31, -15, -1, -17, 33, 16, 1, 32, -63, -31, -1, -33, 65, 32, 1, 36, -71, -35, -1, -37, 73, 36, 1, 44, -87, -43, -1, -45, 89, 44, 1, 48, -95, -47, -1, -49, 97, 48, 1, 80, -159, -79, -1, -81, 161, 80, 1, 84, -167, -83, -1, -85, 169, 84, 1, 92
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118825(k)/A118826(k) are:
at k = 4*n: 1/A080277(n);
at k = 4*n+1: 2/(2*A080277(n)-1);
at k = 4*n+2: 1/(A080277(n)-1);
at k = 4*n-1: 0.
Convergents begin:
-2/1, -1/1, 0/-1, -1/-1, 2/1, 1/0, 0/1, 1/4,
-2/-7, -1/-3, 0/-1, -1/-5, 2/9, 1/4, 0/1, 1/12,
-2/-23, -1/-11, 0/-1, -1/-13, 2/25, 1/12, 0/1, 1/16,
-2/-31, -1/-15, 0/-1, -1/-17, 2/33, 1/16, 0/1, 1/32, ...
		

Crossrefs

Cf. A006519, A080277; A118824 (partial quotients), A118825 (numerators).

Programs

  • PARI
    {a(n)=local(p=-2,q=+1,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[2,1]}

Formula

a(4*n) = (-1)^n*A080277(n); a(4*n+1) = -(-1)^n*(2*A080277(n)-1); a(4*n+2) = -(-1)^n*(A080277(n)-1); a(4*n-1) = (-1)^n.

A118829 Denominators of the convergents of the 2-adic continued fraction of zero given by A118827.

Original entry on oeis.org

1, -2, -1, 2, 1, 0, 1, -8, -7, 6, -1, 10, 9, -8, 1, -24, -23, 22, -1, 26, 25, -24, 1, -32, -31, 30, -1, 34, 33, -32, 1, -64, -63, 62, -1, 66, 65, -64, 1, -72, -71, 70, -1, 74, 73, -72, 1, -88, -87, 86, -1, 90, 89, -88, 1, -96, -95, 94, -1, 98, 97, -96, 1, -160, -159, 158, -1, 162, 161, -160, 1, -168, -167, 166, -1, 170, 169
Offset: 1

Views

Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118828(k)/A118829(k) are:
at k = 4*n: -1/(2*A080277(n));
at k = 4*n+1: -1/(2*A080277(n)-1);
at k = 4*n+2: -1/(2*A080277(n)-2);
at k = 4*n-1: 0.
Convergents begin:
1/1, -1/-2, 0/-1, -1/2, -1/1, 1/0, 0/1, 1/-8,
1/-7, -1/6, 0/-1, -1/10, -1/9, 1/-8, 0/1, 1/-24,
1/-23, -1/22, 0/-1, -1/26, -1/25, 1/-24, 0/1, 1/-32,
1/-31, -1/30, 0/-1, -1/34, -1/33, 1/-32, 0/1, 1/-64, ...
		

Crossrefs

Cf. A118827 (partial quotients), A118829 (denominators).

Programs

  • PARI
    {a(n)=local(p=+1,q=-2,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[1,1]}

Formula

a(4*n) = -(-1)^n*2*A080277(n); a(4*n+1) = -(-1)^n*(2*A080277(n)-1); a(4*n+2) = (-1)^n*(2*A080277(n)-2); a(4*n-1) = (-1)^n.

A118832 Denominators of the convergents of the 2-adic continued fraction of zero given by A118830.

Original entry on oeis.org

1, 2, -1, -2, 1, 0, 1, 8, -7, -6, -1, -10, 9, 8, 1, 24, -23, -22, -1, -26, 25, 24, 1, 32, -31, -30, -1, -34, 33, 32, 1, 64, -63, -62, -1, -66, 65, 64, 1, 72, -71, -70, -1, -74, 73, 72, 1, 88, -87, -86, -1, -90, 89, 88, 1, 96, -95, -94, -1, -98, 97, 96, 1, 160, -159, -158, -1, -162, 161, 160, 1, 168, -167, -166, -1, -170, 169, 168
Offset: 1

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Author

Paul D. Hanna, May 01 2006

Keywords

Examples

			For n>=1, convergents A118831(k)/A118832(k) are:
at k = 4*n: 1/(2*A080277(n));
at k = 4*n+1: 1/(2*A080277(n)-1);
at k = 4*n+2: 1/(2*A080277(n)-2);
at k = 4*n-1: 0.
Convergents begin:
-1/1, -1/2, 0/-1, -1/-2, 1/1, 1/0, 0/1, 1/8,
-1/-7, -1/-6, 0/-1, -1/-10, 1/9, 1/8, 0/1, 1/24,
-1/-23, -1/-22, 0/-1, -1/-26, 1/25, 1/24, 0/1, 1/32,
-1/-31, -1/-30, 0/-1, -1/-34, 1/33, 1/32, 0/1, 1/64, ...
		

Crossrefs

Cf. A080277; A118830 (partial quotients), A118831 (numerators).

Programs

  • PARI
    {a(n)=local(p=-1,q=+2,v=vector(n,i,if(i%2==1,p,q*2^valuation(i/2,2)))); contfracpnqn(v)[2,1]}

Formula

a(4*n) = (-1)^n*2*A080277(n); a(4*n+1) = -(-1)^n*(2*A080277(n)-1); a(4*n+2) = -(-1)^n*(2*A080277(n)-2); a(4*n-1) = (-1)^n.
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