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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A331186 Exponent of the highest power of prime(A067004(n)) which divides n, where A067004 is the ordinal transform of number of divisors of n (A000005).

Original entry on oeis.org

0, 1, 1, 2, 1, 1, 1, 0, 2, 1, 1, 2, 1, 1, 0, 4, 1, 2, 1, 1, 0, 0, 1, 3, 2, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 2, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 4, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 6, 0, 0, 1, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 1, 0, 4, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0
Offset: 1

Views

Author

Antti Karttunen, Jan 12 2020

Keywords

Crossrefs

Programs

  • Mathematica
    b[_] = 0;
    A067004[n_] := A067004[n] = With[{t = DivisorSigma[0, n]}, b[t] = b[t]+1];
    a[n_] := IntegerExponent[n, Prime[A067004[n]]];
    Array[a, 105] (* Jean-François Alcover, Dec 21 2021 *)
  • 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; };
    v067004 = ordinal_transform(vector(up_to,n,numdiv(n)));
    A067004(n) = v067004[n];
    A331186(n) = valuation(n,prime(A067004(n)));

Formula

a(n) = A286561(n, A000040(A067004(n))), where A286561(n,k) gives the k-valuation of n.

A331187 a(n) is n divided by the highest power of prime(A067004(n)) which divides it, where A067004 is the ordinal transform of number of divisors of n (A000005).

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 8, 1, 2, 1, 3, 1, 2, 15, 1, 1, 2, 1, 4, 21, 22, 1, 3, 1, 26, 27, 4, 1, 10, 1, 32, 33, 34, 35, 9, 1, 38, 39, 8, 1, 6, 1, 44, 45, 46, 1, 3, 1, 50, 51, 52, 1, 54, 55, 56, 57, 58, 1, 15, 1, 62, 63, 1, 65, 66, 1, 68, 69, 70, 1, 8, 1, 74, 75, 76, 77, 78, 1, 80, 1, 82, 1, 84, 85, 86, 87, 88, 1, 90
Offset: 1

Views

Author

Antti Karttunen, Jan 12 2020

Keywords

Crossrefs

Cf. also A331185.

Programs

  • Mathematica
    b[_] = 0;
    A067004[n_] := A067004[n] = With[{t = DivisorSigma[0, n]}, b[t] = b[t]+1];
    A331186[n_] := IntegerExponent[n, Prime[A067004[n]]];
    a[n_] := n/(Prime[A067004[n]]^A331186[n]);
    Array[a, 105] (* Jean-François Alcover, Dec 21 2021 *)
  • 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; };
    v067004 = ordinal_transform(vector(up_to,n,numdiv(n)));
    A067004(n) = v067004[n];
    A331187(n) = { my(p=prime(A067004(n))); n/(p^valuation(n,p)); };

Formula

a(n) = n / (A000040(A067004(n))^A331186(n)).
Showing 1-2 of 2 results.