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.

A356758 a(n) is the number of nonzero digits in n!.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 2, 2, 3, 5, 5, 6, 5, 6, 9, 9, 10, 11, 11, 12, 12, 13, 14, 18, 18, 17, 19, 20, 20, 24, 24, 27, 26, 29, 28, 32, 32, 32, 29, 35, 39, 35, 39, 40, 43, 44, 42, 49, 48, 49, 46, 49, 50, 53, 54, 56, 58, 57, 62, 62, 63, 58, 66, 67, 70, 71, 70, 73, 72, 78, 81
Offset: 0

Views

Author

Stefano Spezia, Aug 26 2022

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[IntegerDigits[n!],Positive]],{n,0,70}]
  • PARI
    a(n) = #select(x->(x>0), digits(n!)); \\ Michel Marcus, Aug 26 2022
    
  • Python
    from math import factorial
    def a(n): return len(str(factorial(n)).replace("0", ""))
    print([a(n) for n in range(71)]) # Michael S. Branicky, Aug 26 2022

Formula

a(n) = A034886(n!) - A027869(n!).