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.

A051023 Middle column of rule-30 1-D cellular automaton, from a lone 1 cell.

Original entry on oeis.org

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

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Comments

A092539(n) gives the value of prefix of length n+1, seen as a binary number. - Reinhard Zumkeller, Jun 08 2013
Also middle column of rule 86 1-D cellular automaton, from a lone 1 cell, as rule 86 is the mirror image of rule 30. - Antti Karttunen, Oct 03 2019

Crossrefs

Cf. A070950, A269160 (rule 30), A071032, A269161 (rule 86).
Cf. A327974 (adjacent bits xored), A327982 (partial sums), A327983 (run lengths).
Characteristic function of A327984 (gives the positions of ones in this sequence), A327985 (positions of zeros).
Cf. also A328100, A328101, A328102 (neighbor columns).
Cf. A365254 (converted to base 10).

Programs

  • Haskell
    a051023 n = a070950 n n  -- Reinhard Zumkeller, Jun 06 2013
    
  • Mathematica
    CellularAutomaton[30, {{1}, 0}, 101, {All, {0}}]//Flatten
  • PARI
    A051023(n) = ((A110240(n)>>n)%2);
    \\ Or for fast creation of b-files:
    A051023write(up_to) = { my(s=1, n=0); for(n=0,up_to, write("b051023.txt", n, " ", ((s>>n)%2)); s = A269160(s)); }; \\ Antti Karttunen, Oct 03 2019

Formula

a(n) = A070950(n,n). - Reinhard Zumkeller, Jun 06 2013
a(n) = 1 - A226474(n). - Reinhard Zumkeller, Jun 08 2013
From Antti Karttunen, Oct 04 2019: (Start)
a(n) = A000035(floor(A110240(n) / 2^n)).
For n>= 2, a(n) = (A328100(n) OR A328101(n)) XOR A328101(1+n). ["Sideways evaluation"]
(End)

Extensions

Corrected from 64th term by Daniel B. Cristofani (cristofd(AT)hevanet.com), Jan 07 2004