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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A336842 Number of trailing 1-bits in the binary representation of A003961(n): a(n) = A007814(1+A003961(n)).

Original entry on oeis.org

1, 2, 1, 1, 3, 4, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 3, 6, 3, 3, 1, 3, 1, 2, 1, 2, 5, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 4, 1, 4, 3, 1, 1, 1, 2, 5, 1, 2, 3, 2, 1, 2, 1, 1, 2, 2, 4, 2, 1, 3, 2, 3, 2, 1, 3, 1, 2, 4, 2, 1, 4, 4, 8, 2, 3, 1, 1, 1, 4, 1, 1, 2, 5, 1, 1, 2, 1, 1, 5, 1, 6, 1, 2, 1, 1, 3, 1, 2, 2, 1
Offset: 1

Views

Author

Antti Karttunen, Aug 06 2020

Keywords

Crossrefs

Cf. A003961, A007814, A246261 (positions of ones), A336843, A336844.

Programs

  • PARI
    A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
    A007814(n) = valuation(n,2);
    A336842(n) = A007814(1+A003961(n));
    
  • Python
    from math import prod
    from sympy import factorint, nextprime
    def A336842(n): return (~((m:=prod(nextprime(p)**e for p, e in factorint(n).items()))+1)& m).bit_length() # Chai Wah Wu, Jul 01 2022

Formula

a(n) = A007814(1+A003961(n)).
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