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 1-10 of 27 results. Next

A089809 Complement of A078588.

Original entry on oeis.org

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

Views

Author

Gary W. Adamson, Nov 11 2003

Keywords

Comments

a(n) = 1 if (fractional part of n*r) < 1/2, else a(n) = 0, where r = golden ratio = (1 + sqrt(5))/2. - Clark Kimberling, Dec 27 2016

Examples

			1. a(7) = 1 since A078588(7) = 0
2. a(7) = 1 since A024569 is not 1 (A024569(7) = 3).
3. a(7) = 1 since A089808(7) = 1.
		

Crossrefs

Programs

  • Mathematica
    r = GoldenRatio; z = 500;
    Table[If[FractionalPart[n r] < 1/2, 1, 0 ], {n, 1, z}]  (* A089809 *)
    Table[If[FractionalPart[n r] > 1/2, 1, 0 ], {n, 1, z}]  (* A078588 *)
    1 - % (* A089809,  Clark Kimberling, Dec 27 2016 *)
  • Python
    from math import isqrt
    def A089809(n): return ((n+isqrt(5*n**2))&1)^1 # Chai Wah Wu, Aug 17 2022

Formula

a(n) = 1 if A078588 = 0; otherwise, not.
a(n) = 1 iff A024569 is not 1.
a(n) = 1 iff A089808 is 1.
a(n) = 1 if (fractional part of n*r) < 1/2, else a(n) = 0. - Clark Kimberling, Dec 27 2016

A082848 Duplicate of A078588.

Original entry on oeis.org

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

Views

Author

Keywords

A190427 a(n) = [(b*n+c)*r] - b*[n*r] - [c*r], where (r,b,c)=(golden ratio,2,1) and []=floor.

Original entry on oeis.org

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

Views

Author

Clark Kimberling, May 10 2011

Keywords

Comments

Write a(n) = [(b*n+c)*r] - b*[n*r] - [c*r]. If r>0 and b and c are integers satisfying b>=2 and 0<=c<=b-1, then 0<=a(n)<=b. The positions of 0 in the sequence a are of interest, as are the position sequences for 1,2,...,b. These b+1 position sequences comprise a partition of the positive integers.
Examples:
(golden ratio,2,0): A078588, A005653, A005652
(golden ratio,2,1): A190427 - A190430
(golden ratio,3,0): A140397 - A190400
(golden ratio,3,1): A140431 - A190435
(golden ratio,3,2): A140436 - A190439

Examples

			a(1)=[3r]-2[r]-1=4-3-1=1.
a(2)=[5r]-2[2r]-1=8-6-1=1.
a(3)=[7r]-2[3r]-1=11-8-1=2.
		

Crossrefs

Programs

  • Magma
    [Floor((2*n+1)*(1+Sqrt(5))/2) - 2*Floor(n*(1+Sqrt(5))/2) - 1: n in [1..100]]; // G. C. Greubel, Apr 06 2018
  • Mathematica
    r = GoldenRatio; b = 2; c = 1;
    f[n_] := Floor[(b*n + c)*r] - b*Floor[n*r] - Floor[c*r];
    t = Table[f[n], {n, 1, 320}] (* A190427 *)
    Flatten[Position[t, 0]] (* A190428 *)
    Flatten[Position[t, 1]] (* A190429 *)
    Flatten[Position[t, 2]] (* A190430 *)
    Table[Floor[(2*n+1)*GoldenRatio] - 2*Floor[n*GoldenRatio] -1, {n,1,100}] (* G. C. Greubel, Apr 06 2018 *)
  • PARI
    for(n=1,100, print1(floor((2*n+1)*(1+sqrt(5))/2) - 2*floor(n*(1+sqrt(5))/2) - 1, ", ")) \\ G. C. Greubel, Apr 06 2018
    
  • Python
    from mpmath import mp, phi
    from sympy import floor
    mp.dps=100
    def a(n): return floor((2*n + 1)*phi) - 2*floor(n*phi) - 1
    print([a(n) for n in range(1, 132)]) # Indranil Ghosh, Jul 02 2017
    

Formula

a(n) = [(2*n+1)*r] - 2*[n*r] - 1, where r=(1+sqrt(5))/2.

A005652 Lexicographically least increasing sequence, starting with 1, such that the sum of 2 distinct terms is never a Fibonacci number.

Original entry on oeis.org

1, 3, 6, 8, 9, 11, 14, 16, 17, 19, 21, 22, 24, 27, 29, 30, 32, 35, 37, 40, 42, 43, 45, 48, 50, 51, 53, 55, 56, 58, 61, 63, 64, 66, 69, 71, 74, 76, 77, 79, 82, 84, 85, 87, 90, 92, 95, 97, 98, 100, 103, 105, 106, 108, 110, 111, 113, 116, 118, 119, 121, 124, 126, 129, 131
Offset: 1

Views

Author

Keywords

Comments

Also, k such that k = 2*ceiling(k*phi) - ceiling(k*sqrt(5)) where phi = (1+sqrt(5))/2. - Benoit Cloitre, Dec 05 2002
The Chow-Long paper gives a connection with continued fractions, as well as generalizations and other references for this and related sequences.
Positions of 1's in {A078588(n) : n > 0}. - Clark Kimberling and Jianing Song, Sep 10 2019
Also positive integers k such that {k*r} > 1/2, where r = golden ratio = (1 + sqrt(5))/2 and { } = fractional part. - Clark Kimberling and Jianing Song, Sep 12 2019
The lexicographically least property can be proved with the Walnut theorem prover. - Jeffrey Shallit, Nov 20 2023

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Complement of A005653.
Equals A279934 - 1.
See A078588 for further comments.

Programs

  • Mathematica
    f[n_] := Block[{k = Floor[n/GoldenRatio]}, If[n - k*GoldenRatio > (k + 1)*GoldenRatio - n, 1, 0]]; Select[ Range[131], f[ # ] == 1 &]
    r = (1 + Sqrt[5])/2; z = 300;
    t = Table[Floor[2 n*r] - 2 Floor[n*r], {n, 1, z}] (* {A078588(n) : n > 0} *)
    Flatten[Position[t, 0]] (* A005653 *)
    Flatten[Position[t, 1]] (* this sequence *)
    (* Clark Kimberling and Jianing Song, Sep 10 2019 *)
    r = GoldenRatio;
    t = Table[If[FractionalPart[n*r] < 1/2, 0, 1 ], {n, 1, 120}] (* {A078588(n) : n > 0} *)
    Flatten[Position[t, 0]] (* A005653 *)
    Flatten[Position[t, 1]] (* this sequence *)
    (* Clark Kimberling and Jianing Song, Sep 12 2019 *)

Formula

The set of all k such that the integer multiple of (1+sqrt(5))/2 nearest k is greater than k (Chow-Long).
Numbers k such that 2*{k*phi} - {2k*phi} = 1, where { } denotes fractional part. - Clark Kimberling, Jan 01 2007
Positive integers k such that A078588(k) = 1. - Clark Kimberling and Jianing Song, Sep 10 2019

Extensions

Extended by Robert G. Wilson v, Dec 02 2002
Definition clarified by Jeffrey Shallit, Nov 19 2023

A005653 Lexicographically least increasing sequence, starting with 2, such that the sum of two distinct terms of the sequence is never a Fibonacci number.

Original entry on oeis.org

2, 4, 5, 7, 10, 12, 13, 15, 18, 20, 23, 25, 26, 28, 31, 33, 34, 36, 38, 39, 41, 44, 46, 47, 49, 52, 54, 57, 59, 60, 62, 65, 67, 68, 70, 72, 73, 75, 78, 80, 81, 83, 86, 88, 89, 91, 93, 94, 96, 99, 101, 102, 104, 107, 109, 112, 114, 115, 117, 120, 122, 123, 125, 127, 128
Offset: 1

Views

Author

Keywords

Comments

The Chow-Long paper gives a connection with continued fractions, as well as generalizations and other references for this and related sequences.
Positions of 0's in {A078588(n) : n > 0}. - Clark Kimberling and Jianing Song, Sep 10 2019
Also positive integers k such that {k*r} < 1/2, where r = golden ratio = (1 + sqrt(5))/2 and { } = fractional part. - Clark Kimberling and Jianing Song, Sep 12 2019
Jon E. Schoenfield conjectured, and Jeffrey Shallit proved (using the Walnut theorem prover) the characterization in the title. - Jeffrey Shallit, Nov 19 2023

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Complement of A005652. See A078588 for further comments.

Programs

  • Mathematica
    f[n_] := Block[{k = Floor[n/GoldenRatio]}, If[n - k*GoldenRatio > (k + 1)*GoldenRatio - n, 1, 0]]; Select[ Range[130], f[ # ] == 0 &]
    r = (1 + Sqrt[5])/2; z = 300;
    t = Table[Floor[2 n*r] - 2 Floor[n*r], {n, 1, z}] (* {A078588(n) : n > 0} *)
    Flatten[Position[t, 0]] (* this sequence *)
    Flatten[Position[t, 1]] (* A005652 *)
    (* Clark Kimberling and Jianing Song, Sep 10 2019 *)
    r = GoldenRatio;
    t = Table[If[FractionalPart[n*r] < 1/2, 0, 1 ], {n, 1, 120}] (* {A078588(n) : n > 0} *)
    Flatten[Position[t, 0]] (* this sequence *)
    Flatten[Position[t, 1]] (* A005652 *)
    (* Clark Kimberling and Jianing Song, Sep 12 2019 *)

Formula

The set of all n such that the integer multiple of (1+sqrt(5))/2 nearest n is less than n (Chow-Long).
Numbers n such that 2{n*phi}={2n*phi}, where { } denotes fractional part. - Clark Kimberling, Jan 01 2007
Positive integers such that A078588(n) = 0. - Clark Kimberling and Jianing Song, Sep 10 2019

Extensions

Extended by Robert G. Wilson v, Dec 02 2002
Definition clarified by Jeffrey Shallit, Nov 19 2023

A140397 a(n) = floor(3*phi*n) - 3*floor(phi*n) where phi = (1+sqrt(5))/2.

Original entry on oeis.org

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

Views

Author

Fred Lunnon, Jun 20 2008

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_]:=Floor[3GoldenRatio*n]-3Floor[GoldenRatio*n];Array[a,99] (* James C. McMahon, Jul 08 2025 *)
  • PARI
    a(n) = my(fhi=(1+sqrt(5))/2); floor(3*fhi*n) - 3*floor(fhi*n); \\ Michel Marcus, Aug 26 2013

Formula

a(n) = floor(n*s^2)-floor(s*floor(n*s)), where s=1+phi.

A191329 (Lower Wythoff sequence mod 2)+(Upper Wythoff sequence mod 2).

Original entry on oeis.org

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

Views

Author

Clark Kimberling, May 31 2011

Keywords

Comments

Let r=(golden ratio)=(1+sqrt(5))/2 and let [ ]=floor. Let u(n)=[nr] and v(n)=n+[nr], so that u=A000201, v=A001950, the Wythoff sequences, and A191329=(u mod 2)+(v mod 2)=(number of odd numbers in {[nr],[ns]}).
The sequence A191329 can also be obtained by placing 1 before each term of 2*A078588.

Examples

			u = (1,3,4,6,8,9,...)... = (1,1,0,0,0,1,...) in mod 2
v = (2,5,7,10,13,15,...) = (0,1,1,0,1,1,...) in mod 2,
so that......... A191329 = (1,2,1,0,1,2,...).
		

Crossrefs

Programs

  • Mathematica
    r = GoldenRatio; s = r/(r - 1); h = 500;
    u = Table[Floor[n*r], {n, 1, h}]  (* A000201 *)
    v = Table[Floor[n*s], {n, 1, h}]  (* A001950 *)
    w = Mod[u, 2] + Mod[v, 2]  (* A191329 *)
    b = Flatten[Position[w, 0]]  (* A191330=2*A005653 *)
    c = Flatten[Position[w, 1]]  (* A005408, the odds *)
    d = Flatten[Position[w, 2]]  (* A191331=2*A005652 *)
    e = b/2; (* A005653 *)
    f = d/2; (* A005652 *)
    x = (1/3)^b; z = (1/3)^d;
    k[n_] := x[[n]]; x1 = Sum[k[n], {n, 1, 100}];
    N[x1, 100]
    RealDigits[x1, 10, 100]  (* A191332 *)
    k[n_] := z[[n]]; z1 = Sum[k[n], {n, 1, 100}];
    N[z1, 100]
    RealDigits[z1, 10, 100]  (* A191333 *)
    N[x1 + z1, 100] (* Checks that x1+z1=1/8 *)
    x = (1/3)^e; z = (1/3)^f;
    k[n_] := x[[n]]; x2 = Sum[k[n], {n, 1, 100}];
    N[x2, 100]
    RealDigits[x2, 10, 100]  (* A191334 *)
    k[n_] := z[[n]]; z2 = Sum[k[n], {n, 1, 100}];
    N[z2, 100]
    RealDigits[z2, 10, 100]  (* A191335 *)
    N[x2 + z2, 100] (* checks that x2+z2=1/2 *)
  • PARI
    A191329(n) = { my(y=n+sqrtint(n^2*5)); (((y+n+n)\2)%2) + ((y%4)>1); }; \\ (after programs in A001950 and A085002) - Antti Karttunen, May 19 2021
    
  • Python
    from math import isqrt
    def A191329(n): return m if (m:=((n+isqrt(5*n**2))&2)+(n&1))<3 else 1 # Chai Wah Wu, Aug 10 2022

Formula

a(n) = (A000201(n) mod 2) + (A001950(n) mod 2).
a(n) = A085002(n) + A171587(n). - Michel Dekking, Jan 28 2021

A229829 Numbers coprime to 15.

Original entry on oeis.org

1, 2, 4, 7, 8, 11, 13, 14, 16, 17, 19, 22, 23, 26, 28, 29, 31, 32, 34, 37, 38, 41, 43, 44, 46, 47, 49, 52, 53, 56, 58, 59, 61, 62, 64, 67, 68, 71, 73, 74, 76, 77, 79, 82, 83, 86, 88, 89, 91, 92, 94, 97, 98, 101, 103, 104, 106, 107, 109, 112, 113, 116, 118, 119
Offset: 1

Views

Author

Gary Detlefs, Oct 01 2013

Keywords

Comments

A001651 INTERSECT A047201.
a(n) - 15*floor((n-1)/8) - 2*((n-1) mod 8) has period 8, repeating [1,0,0,1,0,1,1,0].
Numbers whose odd part is 7-rough: products of terms of A007775 and powers of 2 (terms of A000079). - Peter Munn, Aug 04 2020
The asymptotic density of this sequence is 8/15. - Amiram Eldar, Oct 18 2020

Crossrefs

Lists of numbers coprime to other semiprimes: A007310 (6), A045572 (10), A162699 (14), A160545 (21), A235933 (35).
Subsequence of: A001651, A047201.
Subsequences: A000079, A007775.

Programs

  • Magma
    [n: n in [1..120] | IsOne(GCD(n,15))]; // Bruno Berselli, Oct 01 2013
    
  • Maple
    for n from 1 to 500 do if n mod 3<>0 and n mod 5<>0 then print(n) fi od
  • Mathematica
    Select[Range[120], GCD[#, 15] == 1 &] (* or *) t = 70; CoefficientList[Series[(1 + x + 2 x^2 + 3 x^3 + x^4 + 3 x^5 + 2 x^6 + x^7 + x^8)/((1 - x)^2 (1 + x) (1 + x^2) (1 + x^4)) , {x, 0, t}], x] (* Bruno Berselli, Oct 01 2013 *)
    Select[Range[120],CoprimeQ[#,15]&] (* Harvey P. Dale, Oct 31 2013 *)
  • Sage
    [i for i in range(120) if gcd(i, 15) == 1] # Bruno Berselli, Oct 01 2013

Formula

a(n+8) = a(n) + 15.
a(n) = 15*floor((n-1)/8) +2*f(n) +floor(2*phi*(f(n+1)+2)) -2*floor(phi*(f(n+1)+2)), where f(n) = (n-1) mod 8 and phi=(1+sqrt(5))/2.
a(n) = 15*floor((n-1)/8) +2*f(n) +floor((2*f(n)+5)/5) -floor((f(n)+2)/3), where f(n) = (n-1) mod 8.
From Bruno Berselli, Oct 01 2013: (Start)
G.f.: x*(1 +x +2*x^2 +3*x^3 +x^4 +3*x^5 +2*x^6 +x^7 +x^8) / ((1-x)^2*(1+x)*(1+x^2)*(1+x^4)). -
a(n) = a(n-1) +a(n-8) -a(n-9) for n>9. (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = 2*sqrt(7 + sqrt(5) - sqrt(6*(5 + sqrt(5))))*Pi/15. - Amiram Eldar, Dec 13 2021

A190440 [(bn+c)r]-b[nr]-[cr], where (r,b,c)=(golden ratio,4,0) and []=floor.

Original entry on oeis.org

2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 3, 1, 0, 2, 1, 3, 2, 0, 2, 1, 3, 2, 0
Offset: 1

Views

Author

Clark Kimberling, May 10 2011

Keywords

Comments

Write a(n)=[(bn+c)r]-b[nr]-[cr]. If r>0 and b and c are integers satisfying b>=2 and 0<=c<=b-1, then 0<=a(n)<=b. The positions of 0 in the sequence a are of interest, as are the position sequences for 1,2,...,b. These b+1 position sequences comprise a partition of the positive integers.
Examples:
(golden ratio,2,0): A078588, A005653, A005652
(golden ratio,2,1): A190427-A190430
(golden ratio,3,0): A140397-A190400
(golden ratio,3,1): A140431-A190435
(golden ratio,3,2): A140436-A190439

Crossrefs

Programs

  • Mathematica
    r = GoldenRatio;
    f[n_] := Floor[4*n*r] - 4*Floor[n*r];
    t = Table[f[n], {n, 1, 320}] (* A190440 *)
    Flatten[Position[t, 0]]  (* A190240 *)
    Flatten[Position[t, 1]]  (* A190249 *)
    Flatten[Position[t, 2]]  (* A190442 *)
    Flatten[Position[t, 3]]  (* A190443 *)
    Flatten[Position[t, 4]]  (* A190248 *)

Formula

a(n)=[4nr]-4[nr], where r=golden ratio.

A024569 [ 1/{n*r} ], where r = (1 + sqrt(5))/2 and {x} := x - [ x ].

Original entry on oeis.org

1, 4, 1, 2, 11, 1, 3, 1, 1, 5, 1, 2, 29, 1, 3, 1, 1, 8, 1, 2, 1, 1, 4, 1, 2, 14, 1, 3, 1, 1, 6, 1, 2, 76, 1, 4, 1, 2, 9, 1, 2, 1, 1, 5, 1, 2, 21, 1, 3, 1, 1, 7, 1, 2, 1, 1, 4, 1, 2, 12, 1, 3, 1, 1, 5, 1, 2, 38, 1, 3, 1, 2, 8, 1, 2, 1, 1, 4, 1, 2, 16, 1, 3, 1, 1, 6, 1, 2, 199, 1, 4, 1, 2, 10
Offset: 1

Views

Author

Keywords

Comments

A024569(n) = 1 iff A078588 = 1. A024569(n) = 1 iff A089808 is not 1. Either A024569(n) or A089809(n) = 1, but not both. A024569(n) is the complement of A089809(n). - Gary W. Adamson, Nov 11 2003

Crossrefs

Programs

  • Mathematica
    Table[Floor[1/FractionalPart[n*GoldenRatio]], {n, 100}] (* Clark Kimberling, Aug 15 2012 *)

Extensions

Corrected by Clark Kimberling, Aug 15 2012
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