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.

Showing 1-3 of 3 results.

A328845 The first Fibonacci based variant of arithmetic derivative: a(p) = A000045(p) for prime p, a(u*v) = a(u)*v + u*a(v), with a(0) = a(1) = 0.

Original entry on oeis.org

0, 0, 1, 2, 4, 5, 7, 13, 12, 12, 15, 89, 20, 233, 33, 25, 32, 1597, 33, 4181, 40, 53, 189, 28657, 52, 50, 479, 54, 80, 514229, 65, 1346269, 80, 289, 3211, 100, 84, 24157817, 8381, 725, 100, 165580141, 127, 433494437, 400, 105, 57337, 2971215073, 128, 182, 125, 4825, 984, 53316291173, 135, 500, 188, 12581, 1028487, 956722026041, 160
Offset: 0

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Author

Antti Karttunen, Oct 28 2019

Keywords

Crossrefs

Cf. A374046 (indices of even terms), A374047 (of odd terms), A374122 (of multiples of 3), A374202 (2-adic valuation), A374203 (3-adic valuation), A374205 (5-adic valuation), A374125 [a(n) mod 360].
Cf. A374106 [gcd(a(n), A113177(n))], A374035 [gcd(a(n), A328846(n))], A374116 [gcd(a(n), A328768(n))].
For variants of the same formula, see A003415, A258851, A328768, A328769, A328846, A371192.

Programs

  • Mathematica
    A328845[n_] := If[n <= 1, 0, n*Total[MapApply[#2*Fibonacci[#]/# &, FactorInteger[n]]]];
    Array[A328845, 100, 0] (* Paolo Xausa, Dec 16 2024 *)
  • PARI
    A328845(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]*fibonacci(f[i,1])/f[i, 1]));

Formula

a(n) = n * Sum e_j * A000045(p_j)/p_j for n = Product p_j^e_j.
a(A000040(n)) = A030426(n).
A007895(a(n)) = A328847(n).

A374202 The 2-adic valuation of A328845(n), where A328845 is a Fibonacci-based variant of the arithmetic derivative.

Original entry on oeis.org

0, 1, 2, 0, 0, 0, 2, 2, 0, 0, 2, 0, 0, 0, 5, 0, 0, 0, 3, 0, 0, 0, 2, 1, 0, 1, 4, 0, 0, 0, 4, 0, 0, 2, 2, 0, 0, 0, 2, 0, 0, 0, 4, 0, 0, 0, 7, 1, 0, 0, 3, 0, 0, 2, 2, 0, 0, 0, 5, 0, 0, 0, 6, 1, 0, 0, 3, 0, 0, 0, 2, 0, 0, 3, 5, 1, 0, 0, 4, 3, 0, 0, 3, 1, 0, 0, 2, 0, 0, 3, 5, 0, 0, 3, 4, 0, 0, 0, 2, 0, 0, 0, 2, 1, 0, 0, 2
Offset: 2

Views

Author

Antti Karttunen, Jul 01 2024

Keywords

Crossrefs

Cf. A007814, A328845, A374045, A374046 (after its 2 initial terms, gives the indices of nonzero terms in this sequence), A374047 (indices of 0's).

Programs

  • Mathematica
    A374202[n_] := IntegerExponent[n*Total[MapApply[#2*Fibonacci[#]/# &, FactorInteger[n]]], 2];
    Array[A374202, 100, 2] (* Paolo Xausa, Dec 16 2024 *)
  • PARI
    A328845(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]*fibonacci(f[i,1])/f[i, 1]));
    A374202(n) = valuation(A328845(n), 2);

Formula

a(n) = A007814(A328845(n)).

A374207 The 3-adic valuation of A113177(n), where A113177 is fully additive with a(p) = Fibonacci(p).

Original entry on oeis.org

0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 0, 0, 0, 2, 1, 1, 0, 0, 0, 0, 0, 0, 2, 1, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 3, 1, 0, 1, 0, 0, 2, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 3, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0
Offset: 2

Views

Author

Antti Karttunen, Jul 01 2024

Keywords

Crossrefs

Cf. A007949, A113177, A374051, A374052 (indices of nonzero terms).

Programs

  • PARI
    A113177(n) = if(n<=1, 0, my(f=factor(n)); sum(i=1, #f~, f[i, 2]*fibonacci(f[i,1])));
    A374207(n) = valuation(A113177(n), 3);

Formula

a(n) = A007949(A113177(n)).
Showing 1-3 of 3 results.