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.

A325226 Number of prime factors of n that are less than the largest, counted with multiplicity.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 2, 0, 1, 1, 0, 0, 1, 0, 2, 1, 1, 0, 3, 0, 1, 0, 2, 0, 2, 0, 0, 1, 1, 1, 2, 0, 1, 1, 3, 0, 2, 0, 2, 2, 1, 0, 4, 0, 1, 1, 2, 0, 1, 1, 3, 1, 1, 0, 3, 0, 1, 2, 0, 1, 2, 0, 2, 1, 2, 0, 3, 0, 1, 1, 2, 1, 2, 0, 4, 0, 1, 0, 3, 1, 1, 1, 3, 0, 3, 1, 2, 1, 1, 1, 5, 0, 1, 2, 2, 0, 2, 0, 3, 2
Offset: 1

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Author

Gus Wiseman, Apr 12 2019

Keywords

Examples

			The prime factors of 300 are {2,2,3,5,5} of which {2,2,3} are less than the largest, so a(300) = 3.
		

Crossrefs

Positions of 0's are A000961. Positions of 1's are A325230. Positions of terms > 1 are A307517.

Programs

  • Mathematica
    Table[PrimeOmega[n/Power@@FactorInteger[n][[-1]]],{n,100}]
  • PARI
    A071178(n) = if(1==n, 0, factor(n)[omega(n), 2]);
    A325226(n) = (bigomega(n) - A071178(n)); \\ Antti Karttunen, Nov 17 2019

Formula

a(n) = A001222(n/A053585(n)).
a(n) = A001222(n) - A071178(n) = A062977(A108951(n)). - Antti Karttunen, Nov 17 2019

Extensions

Data section extended up to term a(105) by Antti Karttunen, Nov 17 2019