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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A335063 a(n) = Sum_{k=0..n} (binomial(n,k) mod 2) * k.

Original entry on oeis.org

0, 1, 2, 6, 4, 10, 12, 28, 8, 18, 20, 44, 24, 52, 56, 120, 16, 34, 36, 76, 40, 84, 88, 184, 48, 100, 104, 216, 112, 232, 240, 496, 32, 66, 68, 140, 72, 148, 152, 312, 80, 164, 168, 344, 176, 360, 368, 752, 96, 196, 200, 408, 208, 424, 432, 880, 224, 456, 464, 944, 480
Offset: 0

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Author

Ilya Gutkovskiy, May 21 2020

Keywords

Comments

Modulo 2 binomial transform of nonnegative integers.

Crossrefs

Programs

  • Maple
    g:= proc(n,k) local L,M,t,j;
       L:= convert(k,base,2);
       M:= convert(n,base,2);
       1-max(zip(`*`,L,M))
    end proc:
    f:= n -> add(k*g(n-k,k),k=0..n):
    map(f, [$0..100]); # Robert Israel, May 24 2020
  • Mathematica
    Table[Sum[Mod[Binomial[n, k], 2] k, {k, 0, n}], {n, 0, 60}]
    (* or *)
    nmax = 60; CoefficientList[Series[(x/2) D[Product[(1 + 2 x^(2^k)), {k, 0, Log[2, nmax]}], x], {x, 0, nmax}], x]
  • PARI
    a(n) = n*2^(hammingweight(n)-1); \\ Michel Marcus, May 22 2020

Formula

G.f.: (x/2) * (d/dx) Product_{k>=0} (1 + 2 * x^(2^k)).
a(n) = n * 2^(A000120(n) - 1) = n * A001316(n) / 2.
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