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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A230598 Lexicographically earliest sequence of distinct positive integers such that all black pixels in the binary plot of the sequence are connected (see Comments for details).

Original entry on oeis.org

1, 3, 2, 6, 4, 5, 7, 9, 11, 10, 14, 8, 12, 13, 15, 17, 19, 18, 22, 20, 21, 23, 25, 27, 26, 30, 16, 24, 28, 29, 31, 33, 35, 34, 38, 36, 37, 39, 41, 43, 42, 46, 40, 44, 45, 47, 49, 51, 50, 54, 52, 53, 55, 57, 59, 58, 62, 32, 48, 56, 60, 61, 63, 65, 67, 66, 70
Offset: 1

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Author

Paul Tek, Oct 24 2013

Keywords

Comments

For any n, m, i, j such that a(n) AND (2^i) <> 0, and a(m) AND (2^j) <>0 (where AND stands for the bitwise AND operator), there exist two sequences of finite length L, say p and b, such that:
(1) p(1)=n, b(1)=i,
(2) p(L)=m, b(L)=j,
(3) a(p(k)) AND (2^b(k)) <> 0 for any k between 1 and L,
(4) |p(k+1)-p(k)| + |b(k+1)-b(k)| = 1 for any k between 1 and L-1.
These two finite sequences define a path of black pixels connecting the black pixels at positions (n,i) and (m,j).

Crossrefs

Programs

  • Perl
    See Link section.

Formula

Empirically, for any k>2 :
(1) a(2^k-1) = 2^k-1,
(2) a(2^k) = 2^k+1,
(3) a(n) = a(n-2^k+1) + 2^k, for any n such that 2^k<=n<2^(k+1)-(k+1),
(4) a(n) = 2^k, for n=2^(k+1)-(k+1),
(5) a(n) = a(n-2^k) + 2^k, for any n such that 2^(k+1)-(k+1)
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