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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A175312 Maximum value on Lower Shuffle Part of Kimberling's Expulsion Array (A035486).

Original entry on oeis.org

1, 3, 5, 7, 10, 12, 15, 17, 20, 22, 25, 28, 31, 33, 36, 39, 42, 44, 47, 50, 53, 55, 58, 61, 64, 67, 70, 73, 76, 78, 81, 84, 87, 90, 93, 96, 99, 101, 104, 107, 110, 113, 116, 119, 122, 124, 127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 169, 171
Offset: 1

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Author

Enrique Pérez Herrero, Mar 28 2010

Keywords

Comments

a(n) is the maximum value on or below diagonal of Kimberling's Expulsion Array; this part could be called the Lower Shuffle.

References

  • D. Gale, Tracking the Automatic Ant: And Other Mathematical Explorations, ch. 5, p. 27. Springer, 1998
  • R. K. Guy, Unsolved Problems Number Theory, Sect E35.

Crossrefs

Programs

  • Mathematica
    (* By direct computation *)
    K[i_, j_] := i + j - 1 /; (j >= 2 i - 3);
    K[i_, j_] := K[i - 1, i - (j + 2)/2] /; (EvenQ[j] && (j < 2 i - 3));
    K[i_, j_] := K[i - 1, i + (j - 1)/2] /; (OddQ[j] && (j < 2 i - 3));
    K[i_] := K[i] = K[i, i]; SetAttributes[K, Listable];
    A175312[n_] := Max[Table[K[n, i], {i, 1, n}]]  (* Enrique Pérez Herrero, Mar 30 2010 *)
    (* By the Formula *)
    \[Lambda][n_] := Floor[Log[2, (n + 2)/3]];
    A175312[n_] := 1 + 3*(n - \[Lambda][n]) - Floor[(n + 2)/(2^\[Lambda][n])] (* Enrique Pérez Herrero, Mar 30 2010 *)
  • PARI
    lambda(n)= floor(log((n + 2)/3)/log(2));
    A175312(n)= 1 + 3*(n - lambda(n)) - floor((n + 2)/(2^lambda(n))); \\ Enrique Pérez Herrero, Mar 30 2010

Formula

a(n) = 1 + 3(n-lambda(n)) - floor((n+2)/2^lambda(n)), lambda(n) = floor(log_2((n+2)/3)).
a(n) >= A007063(n); a(n) = max(K(n,1),K(n,2),...,K(n,n)), where K(i,j) is an element of Kimberling's Array given by A035486.
From Enrique Pérez Herrero, Mar 30 2010: (Start)
a(theta(k)) = A007063(theta(k)), where theta(k) = Sum_{i=0..k-1} 2^floor(i/3).
At these values the maximum in the Lower Shuffle is the diagonal expelled element. (End)

A035505 Active part of Kimberling's expulsion array as a triangular array.

Original entry on oeis.org

4, 2, 6, 2, 7, 4, 8, 7, 9, 2, 10, 6, 6, 2, 11, 9, 12, 7, 13, 8, 13, 12, 8, 9, 14, 11, 15, 2, 16, 6, 2, 11, 16, 14, 6, 9, 17, 8, 18, 12, 19, 13, 18, 17, 12, 9, 19, 6, 13, 14, 20, 16, 21, 11, 22, 2, 16, 14, 21, 13, 11, 6, 22, 19, 2, 9, 23, 12, 24, 17, 25, 18, 23, 2, 12, 19, 24, 22, 17, 6
Offset: 1

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Author

Keywords

Comments

Active or shuffle part of Kimberling's expulsion array (A035486) is given by the elements K(i,j), where j < 2*i-3. [Enrique Pérez Herrero, Apr 14 2010]

Examples

			4 2; 6 2 7 4; 8 7 9 2 10 6; ...
		

References

  • R. K. Guy, Unsolved Problems Number Theory, Sect. E35.

Crossrefs

Programs

  • Mathematica
    A000194[n_] := Floor[(1 + Sqrt[4 n - 3])/2];
    A074294[n_] := n - 2*Binomial[Floor[1/2 + Sqrt[n]], 2];
    K[i_, j_] := i + j - 1 /; (j >= 2 i - 3);
    K[i_, j_] := K[i - 1, i - (j + 2)/2] /; (EvenQ[j] && (j < 2 i - 3));
    K[i_, j_] := K[i - 1, i + (j - 1)/2] /; (OddQ[j] && (j < 2 i - 3));
    A035505[n_] := K[A000194[n] + 2, A074294[n]]
    (* Enrique Pérez Herrero, Apr 14 2010 *)

Formula

From Enrique Pérez Herrero, Apr 14 2010: (Start)
a(n) = K(A000194(n)+2, A074294(n)), where
K(i,j) = i + j - 1; (j >= 2*i - 3)
K(i,j) = K(i-1, i-(j+2)/2) if j is even and j < 2*i - 3
K(i,j) = K(i-1, i+(j-1)/2); if j is odd and j < 2*i - 3.
(End)

Extensions

More terms from James Sellers, Dec 23 1999

A282348 Numbers expelled during the formation of the array A282347.

Original entry on oeis.org

1, 3, 5, 2, 8, 9, 4, 10, 7, 20, 12, 24, 14, 23, 29, 31, 18, 28, 22, 47, 39, 38, 46, 57, 11, 41, 27, 6, 55, 66, 63, 76, 69, 59, 15, 34, 53, 70, 79, 104, 99, 48, 97, 58, 89, 25, 13, 126, 87, 30, 115, 82, 91, 52, 143, 67, 95, 75, 123, 64, 37, 86, 44, 169, 88, 113
Offset: 1

Views

Author

Clark Kimberling, Feb 13 2017

Keywords

Crossrefs

Programs

  • Mathematica
    f[seq_] := Riffle[Take[Reverse[seq], #], Take[seq, #]] &[Floor[Length[seq]/2]];
    rows = 200; row[1] = Table[n, {n, rows}];
    Table[row[n + 1] = Flatten[{f[Take[row[n], 2 n - 1]], Drop[row[n], 2 n - 1]}], {n, Floor[(rows - 1)/3 + 1]}];
    TableForm[Table[Take[row[n], 20], {n, 1, 20}]] (* A282347 *)
    Table[row[n][[n]], {n, 2 + Floor[(rows - 1)/3]}] (* A282348 *)

A038834 Past of komet 'k2' (A038807).

Original entry on oeis.org

2, 25, 43, 1523, 1833, 1016, 105511, 39366, 19872, 163433, 576843397, 335121400, 338128753, 173216346, 792656991
Offset: 0

Views

Author

Keywords

Crossrefs

Formula

a(0) = 2; a(n) = a(n-1)-th term in Kimberling's sequence A006852.

A307536 Self referencing version of the "Kimberling shuffle" sequence (see Comments).

Original entry on oeis.org

1, 2, 2, 4, 2, 6, 6, 8, 2, 2, 11, 2, 13, 14, 6, 6, 2, 11, 19, 2, 21, 6, 2, 2, 2, 26, 27, 6, 11, 26, 13, 11, 19, 19, 11, 2, 26, 26, 13, 40, 26, 2, 2, 13, 45, 2, 26, 19, 49, 50, 51, 51, 21, 13, 26, 2, 57, 26, 6, 13, 2, 27, 63, 57, 26, 6, 21, 26, 21, 11, 26, 40, 73, 74, 45, 11, 77, 78, 2, 80, 6, 49, 2, 2, 85, 73, 87, 27, 89
Offset: 1

Views

Author

David James Sycamore, Apr 12 2019

Keywords

Comments

If the first row of the expulsion array is replaced by this sequence, and the rows are "shuffled" then the sequence reappears in the diagonal.
For integer n >= 1 define the set [n]={x; A^r(x)=n}U{y; B^r(y)=n}; (r=0,1,2,3..., A^0(n)=B^0(n)=n), where A=A007063 and B=A006852 (mutual inverses). This set includes n, together with all numbers linked to n by A and B. If a number m is in [n], then [m]=[n], therefore we name the set by its least element k, which takes the following values: 1,2,4,6,8,11,13,14,19,21,26,27,40,45,48,50,51,57,63,... Assuming every n is a term in A, the collection of distinct sets [k] is a partition of the natural numbers, and this sequence is constructed by replacing in the first row of the original array, every number n in [k], with k.
A lexicographically earliest version can be obtained from this sequence by replacing any term > all preceding terms by k+1, where k is the greatest term seen so far. Thus: 1,2,2,3,2,4,4,5,2,2,6,2,7,8,4,4,2,6,9,2,10,4,2,2,2,11,...
From Lars Blomberg, Apr 27 2019: (Start)
Starting with some k value and extending in both directions using A and B results in a "valley" with k at the bottom and often sub-valleys on the hillsides (larger than k). (See the document referenced in A038807 for an illustration.)
So the k sequence is computed by selecting the smallest value not yet seen and iterate as far as possible, then select the next value not seen, etc.
However, while it seems that A and B values goes toward infinity, it is not known whether a known valley will eventually connect to another known valley, leading to a different set of k values.
The DATA is based on iterating A and B until the value > 10^8. (End)

Examples

			Examples of [k] for the above list up to k=27:
[1]={1}; so a(1)=1
[2]={2,3,5,9,10,12,17,20,23,24,25,36,42,43,...}; so a(3)=a(5)=a(9)=...=a(43)=2, etc.
[4]={4}; a(4)=4
[6]={6,7,15,16,22,28,59,66,81,...}; a(6)=a(7)=a(15)=...a(81)=6, etc.
[8]={8}; a(8)=8
[11]={11,18,29,32,35,70,76,...}; a(18)=a(29)=...=a(76)=11, etc.
[13]={13,31,39,44,54,60,90,...}; a(31)=a(39)=...=a(90)=13, etc.
[14]={14}; a(14)=14
[19]={19,33,34,48,...}
[21]={21,53,67,69,...}
[26]={26,30,37,38,41,47,55,58,65,68,71,95,99,...}
[27]={27,62,88,...}
		

References

  • R. K. Guy, Unsolved Problems Number Theory, Sect E35.

Crossrefs

Programs

  • PARI
    {A(z) = x=z; y=z; xx=2*x-4; while (y<=xx, x--; xx-=2; if (bittest(y,0)==1, y=x+((y+1)>>1), y=x-(y>>1))); return(x+y-1);};
    {B(z) = a=z; n=1; while (a!=n, if (a2*n, a--, a=2*(a-n)-1);n++); return(a);}; \\ Lars Blomberg, Apr 29 2019

A307797 Lexicographically earliest version of a self referencing "Kimberling shuffle" expulsion array sequence.

Original entry on oeis.org

1, 2, 2, 3, 2, 4, 4, 5, 2, 2, 6, 2, 7, 8, 4, 4, 2, 6, 9, 2, 10, 4, 2, 2, 2, 11, 12, 4, 6, 11, 7, 6, 9, 9, 6, 2, 11, 11, 7, 13, 11, 2, 2, 7, 14, 2, 11, 9, 15, 16, 17, 17, 10, 7, 11, 2, 18, 11, 4, 7, 2, 12, 19, 18, 11, 4, 10, 11, 10, 6, 11, 13, 20, 21, 14, 6, 22, 23, 2, 24, 4, 15, 2, 2, 25, 20, 26, 12, 27, 7, 16, 28, 29, 30, 11, 31, 13, 29, 11
Offset: 1

Views

Author

Keywords

Comments

Start with this sequence, "shuffle" as in A007063 and the sequence reappears in the diagonal of the array. Terms are transformed from A307536 to this lexicofirst version by replacing the first and all subsequent occurrences of any term > all preceding terms by k+1, where k is the greatest (transformed) term seen so far. The records of this sequence is the natural numbers, A000027, starting point of the original Kimberling exclusion array.

Examples

			A307536(4)=4 > all preceding terms, the greatest of which is 2, so a(4)=3. Since 4 appears only once in A307536, 3 appears only once in this sequence.
A307536(21)=21 > all preceding terms, the greatest of which (in this sequence) is 9, so a(21)=10. Subsequent terms with the same value are a(53), a(67), a(69), ... because the corresponding terms (same indices) in A307536 all have value 21.
		

Crossrefs

Programs

  • PARI
    A(z) = {x=z; y=z; xx=2*x-4; while (y<=xx, x--; xx-=2; if (bittest(y, 0)==1, y=x+((y+1)>>1), y=x-(y>>1))); return(x+y-1); } \\ A007063
    B(z) = {a=z; n=1; while (a!=n, if (a2*n, a--, a=2*(a-n)-1); n++); return(a);} \\ A006852
    addgroup(group, n, fixed, v) = {my(ok = 1, m=v[n]); while(ok, listput(group, m); if (m==n, ok=0; break); if (m > #v, ok=0; break); n = m; m = v[n];); group;}
    makegroup(n, fixed, va, vb) = {my(group = List()); listput(group, n); group = addgroup(group, n, fixed, va); group = addgroup(group, n, fixed, vb); listsort(group, 1); Vec(group);}
    setgroup(v, n, group) = {my(gmin = vecmin(group)); for (i=1, #group, if ((group[i] <= #v) && !v[n], v[n] = gmin);); v;}
    lista() = {nn = 200; nout = 90; va = vector(nn, k, A(k)); vb = vector(nn, k, B(k)); vc = vector(nn); fixed = List(); for (n = 1, nn, if (va[n] == n, listput(fixed, n));); fixed = Vec(fixed); for (n=1, nn, group = makegroup(n, fixed, va, vb); vc = setgroup(vc, n, group);); vector(nout, k, vc[k]);} \\ A307536
    earliest(v) = {my(m = Map(), val=1); for (i=1, #v, if (!mapisdefined(m, v[i]), mapput(m, v[i], val); val++);); apply(x->mapget(m, x), v);}
    earliest(lista()) \\ Michel Marcus, Jun 14 2019
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