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.

A331744 Lexicographically earliest infinite sequence such that a(i) = a(j) => A009194(i) = A009194(j) and A323901(i) = A323901(j) for all i, j.

Original entry on oeis.org

1, 1, 2, 1, 3, 4, 5, 1, 6, 7, 8, 9, 3, 10, 11, 1, 12, 13, 14, 7, 15, 16, 17, 18, 19, 7, 17, 20, 6, 21, 22, 1, 23, 24, 25, 6, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 9, 30, 19, 37, 7, 15, 38, 39, 40, 41, 42, 14, 43, 41, 44, 22, 1, 45, 46, 47, 24, 48, 49, 50, 13, 51, 52, 53, 54, 55, 56, 57, 7, 58, 59, 60, 61, 62, 63, 64, 33, 65, 66, 67, 68, 69, 70, 71, 18, 69, 30, 72, 19
Offset: 1

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Author

Antti Karttunen, Feb 04 2020

Keywords

Comments

Restricted growth sequence transform of the ordered pair [A009194(n), A323901(n)].

Crossrefs

Programs

  • PARI
    \\ Needs also code from A323901.
    up_to = 65537;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A009194(n) = gcd(n, sigma(n));
    Aux331744(n) = [A009194(n),A323901(n)];
    v331744 = rgs_transform(vector(up_to, n, Aux331744(n)));
    A331744(n) = v331744[n];

Formula

a(2^n) = 1 for all n >= 0.