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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A026600 a(n) is the n-th letter of the infinite word generated from w(1)=1 inductively by w(n)=JUXTAPOSITION{w(n-1),w'(n-1),w"(n-1)}, where w(k) becomes w'(k) by the cyclic permutation 1->2->3->1 and w"(k) = (w')'(k).

Original entry on oeis.org

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

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Keywords

Examples

			1;
(123);
(123)(231)(312);
(123)(231)(312)(231)(312)(123)(312)(123)(231);
		

Crossrefs

Equals A053838(n-1) + 1. Cf. A026601-A026614.

Programs

  • Mathematica
    Nest[ Flatten[ # /. {1 -> {1, 2, 3}, 2 -> {2, 3, 1}, 3 -> {3, 1, 2}}] &, {1}, 7] (* Robert G. Wilson v, Mar 08 2005 *)
  • PARI
    {a(n) = if( n<2, n>0, (a((n + 2)\ 3) + n + 1 )%3 + 1)} /* Michael Somos, Sep 06 2008 */

Formula

a(A026601(n)) = 1.
a(A026602(n)) = 2.
a(A026603(n)) = 3. -Michael Somos, Sep 06 2008

A026601 Numbers k such that A026600(k) = 1.

Original entry on oeis.org

1, 6, 8, 12, 14, 16, 20, 22, 27, 30, 32, 34, 38, 40, 45, 46, 51, 53, 56, 58, 63, 64, 69, 71, 75, 77, 79, 84, 86, 88, 92, 94, 99, 100, 105, 107, 110, 112, 117, 118, 123, 125, 129, 131, 133, 136, 141, 143, 147, 149, 151, 155, 157, 162
Offset: 1

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Author

Keywords

Comments

It appears that a(n) gives the position of its own n-th 1 modulo 3 term, the n-th 2 modulo 3 term in A026602, and the n-th multiple of 3 in A026603. A026602 and A026603 appear to have analogous indexical properties. - Matthew Vandermast, Oct 06 2010
This follows directly from the generating morphism for A026600: a 1 in position k creates a 1 in position 3k-2, a 2 in position 3k-1, and a 3 in position 3k. Since each block of three terms in A026600 is a permutation of {1,2,3}, these created terms are the k-th terms of their respective index sequences. The proof for the other index sequences is similar. - Charlie Neder, Mar 10 2019

Crossrefs

Formula

a(n) = A079498(n) + 1.

A026602 Numbers k such that A026600(k) = 2.

Original entry on oeis.org

2, 4, 9, 10, 15, 17, 21, 23, 25, 28, 33, 35, 39, 41, 43, 47, 49, 54, 57, 59, 61, 65, 67, 72, 73, 78, 80, 82, 87, 89, 93, 95, 97, 101, 103, 108, 111, 113, 115, 119, 121, 126, 127, 132, 134, 137, 139, 144, 145, 150, 152, 156, 158, 160
Offset: 1

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Author

Keywords

Comments

It appears that a(n) gives the position of its own n-th 1 modulo 3 term, the n-th 2 modulo 3 term in A026603, and the n-th multiple of 3 in A026601. A026601 and A026603 appear to have the same sort of indexical properties. - Matthew Vandermast, Oct 06 2010

Crossrefs

A287437 Positions of 2 in A053838.

Original entry on oeis.org

3, 5, 7, 11, 13, 18, 19, 24, 26, 29, 31, 36, 37, 42, 44, 48, 50, 52, 55, 60, 62, 66, 68, 70, 74, 76, 81, 83, 85, 90, 91, 96, 98, 102, 104, 106, 109, 114, 116, 120, 122, 124, 128, 130, 135, 138, 140, 142, 146, 148, 153, 154, 159, 161, 163, 168, 170, 174, 176
Offset: 1

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Author

Clark Kimberling, May 26 2017

Keywords

Comments

a(n) - a(n-1) is in {1,2,3,4,5} for n >= 1; also, 3n - a(n) is in {0, 1, 2} for n >= 1.
Does this differ from A026603? - R. J. Mathar, Jun 14 2017

Crossrefs

Programs

  • Mathematica
    s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 2, 0}, 2->{2, 0, 1}}] &, {0}, 9]; (*A053838*)
    Flatten[Position[s, 0]]; (*A287435*)
    Flatten[Position[s, 1]]; (*A287436*)
    Flatten[Position[s, 2]]; (*A287437*)

Formula

a(n) + A053838(n-1) = 3n.

Extensions

The definition refers to a different offset in A053838. - R. J. Mathar, May 30 2017
Showing 1-4 of 4 results.