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 1-4 of 4 results.

A344432 a(n) = Sum_{k=1..n} mu(k) * 2^(n - k).

Original entry on oeis.org

0, 1, 1, 1, 2, 3, 7, 13, 26, 52, 105, 209, 418, 835, 1671, 3343, 6686, 13371, 26742, 53483, 106966, 213933, 427867, 855733, 1711466, 3422932, 6845865, 13691730, 27383460, 54766919, 109533837, 219067673, 438135346, 876270693, 1752541387, 3505082775, 7010165550
Offset: 0

Views

Author

Seiichi Manyama, May 19 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := Sum[MoebiusMu[k] * 2^(n-k), {k,1,n}]; Array[a, 40] (* Amiram Eldar, May 19 2021 *)
  • PARI
    a(n) = sum(k=1, n, moebius(k)*2^(n-k));
    
  • PARI
    my(N=40, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, moebius(k)*x^k)/(1-2*x)))
    
  • PARI
    a(n) = if(n==0, 0, 2*a(n-1)+moebius(n));

Formula

G.f.: (Sum_{k>=1} mu(k) * x^k) / (1 - 2*x).
a(n) = 2 * a(n-1) + mu(n) for n > 0.
a(n) ~ A238270 * 2^n. - Vaclav Kotesovec, May 19 2021

A344433 a(n) = Sum_{k=1..n} mu(k) * k^(n - k).

Original entry on oeis.org

1, 0, -2, -6, -17, -46, -132, -402, -1314, -4613, -17313, -68893, -288556, -1269637, -5907157, -29489299, -160431708, -955478664, -6145884133, -41584238971, -287650358748, -1984825313901, -13377544470631, -86142095523089, -512881404732949, -2634567148684612, -9205461936290915, 17544751152746927
Offset: 1

Views

Author

Seiichi Manyama, May 19 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := Sum[MoebiusMu[k] * k^(n-k), {k,1,n}]; Array[a, 30] (* Amiram Eldar, May 19 2021 *)
  • PARI
    a(n) = sum(k=1, n, moebius(k)*k^(n-k));
    
  • PARI
    my(N=40, x='x+O('x^N)); Vec(sum(k=1, N, moebius(k)*x^k/(1-k*x)))

Formula

G.f.: Sum_{k>=1} mu(k) * x^k / (1 - k*x).

A292779 Interpret the values of the Moebius function mu(k) for k = n to 1 as a balanced ternary number.

Original entry on oeis.org

1, -2, -11, -11, -92, 151, -578, -578, -578, 19105, -39944, -39944, -571385, 1022938, 5805907, 5805907, -37240814, -37240814, -424661303, -424661303, 3062123098, 13522476301, -17858583308, -17858583308, -17858583308, 829430026135, 829430026135, 829430026135
Offset: 1

Views

Author

Alonso del Arte, Sep 22 2017

Keywords

Comments

Balanced ternary is much like regular ternary, but with the crucial difference of using the digit -1 instead of the digit 2. Then some powers of 3 are added, others are subtracted.
Since the least significant digit is always 1, a(n) is never a multiple of 3.
If mu(n) = 0, then a(n) is the same as a(n - 1).
Run lengths are given by A076259. - Andrey Zabolotskiy, Oct 13 2017

Examples

			mu(1) = 1, so a(1) = 1 * 3^0 = 1.
mu(2) = -1, so a(2) = -1 * 3^1 + 1 * 3^0 = -3 + 1 = -2.
mu(3) = -1, so a(3) = -1 * 3^2 + -1 * 3^1 + 1 * 3^0 = -9 - 3 + 1 = -11.
mu(4) = 0, so a(4) = 0 * 3^3 + -1 * 3^2 + -1 * 3^1 + 1 * 3^0 = -9 - 3 + 1 = -11.
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 0,
          a(n-1)+3^(n-1)*numtheory[mobius](n))
        end:
    seq(a(n), n=1..33);  # Alois P. Heinz, Oct 13 2017
  • Mathematica
    Table[3^Range[0, n - 1].MoebiusMu[Range[n]], {n, 50}]
  • PARI
    a(n) = sum(k=1, n, moebius(k)*3^(k-1)); \\ Michel Marcus, Oct 01 2017

Formula

a(n) = Sum_{k = 1 .. n} mu(k) 3^(k - 1).

A343425 a(n) = Sum_{k=1..n} mu(k) * n^(n - k).

Original entry on oeis.org

1, 1, 5, 44, 474, 6259, 98398, 1801784, 37726398, 889909001, 23363492888, 675898131588, 21367308429609, 732952005073611, 27116443849927291, 1076343749563379984, 45629840631648951966, 2057705657634136459302, 98357762859847238180913
Offset: 1

Views

Author

Seiichi Manyama, May 19 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := Sum[MoebiusMu[k] * n^(n-k), {k,1,n}]; Array[a, 20] (* Amiram Eldar, May 19 2021 *)
  • PARI
    a(n) = sum(k=1, n, moebius(k)*n^(n-k));
Showing 1-4 of 4 results.