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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A348651 Number of ones in the binary expansion of (n!)!.

Original entry on oeis.org

1, 1, 1, 4, 29, 293, 2566, 24844, 259437, 2908263, 35102629, 455204360, 6321171774
Offset: 0

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Author

Alois P. Heinz, Oct 27 2021

Keywords

Examples

			a(3) = 4 because (3!)! = 6! = 720 = 1011010000_2 which has 4 ones.
		

Crossrefs

Programs

  • Maple
    a:= n-> add(i, i=Bits[Split](n!!)):
    seq(a(n), n=0..10);
  • Mathematica
    a[n_] := DigitCount[(n!)!, 2, 1]; Array[a, 10, 0] (* Amiram Eldar, Oct 29 2021 *)
  • PARI
    a(n) = hammingweight((n!)!); \\ Michel Marcus, Oct 29 2021
  • Python
    from gmpy2 import fac, popcount
    def A348651(n): return popcount(fac(fac(n))) # Chai Wah Wu, Oct 28 2021
    

Formula

a(n) = A000120(A000197(n)).

Extensions

a(11)-a(12) from Chai Wah Wu, Oct 28 2021
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