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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A353278 Ordinal transform of the function f(n) = [A020639(n), A341353(n)] for n > 1, with f(1) = 1.

Original entry on oeis.org

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

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Author

Antti Karttunen, Apr 10 2022

Keywords

Comments

Also the ordinal transform of A353277.

Crossrefs

Programs

  • PARI
    up_to = 65537;
    ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
    A007814(n) = valuation(n,2);
    A007949(n) = valuation(n,3);
    A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
    Aux353278(n) = if(1==n,1,my(u=A156552(n)); [A007814(u), A007949(u)]);
    v353278 = ordinal_transform(vector(up_to, n, Aux353278(n)));
    A353278(n) = v353278[n];
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