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.

A381404 a(n) is the mode of the multiset of bases and exponents (including exponents = 1) in the prime factorization of n (using largest mode if multimodal).

Original entry on oeis.org

2, 3, 2, 5, 1, 7, 3, 3, 1, 11, 2, 13, 1, 1, 4, 17, 2, 19, 2, 1, 1, 23, 3, 5, 1, 3, 2, 29, 1, 31, 5, 1, 1, 1, 2, 37, 1, 1, 5, 41, 1, 43, 2, 5, 1, 47, 4, 7, 2, 1, 2, 53, 3, 1, 7, 1, 1, 59, 2, 61, 1, 7, 6, 1, 1, 67, 2, 1, 1, 71, 3, 73, 1, 5, 2, 1, 1, 79, 5, 4, 1, 83, 2, 1, 1
Offset: 2

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Author

Paolo Xausa, Feb 27 2025

Keywords

Examples

			The prime factorization of 132 is 2^2*3^1*11^1, the multiset of these bases and exponents is {1, 1, 2, 2, 3, 11} and its largest most frequent element is 2.
		

Crossrefs

Cf. A000040 (fixed points).

Programs

  • Mathematica
    A381404[n_] := Max[Commonest[Flatten[FactorInteger[n]]]];
    Array[A381404, 100, 2]

Formula

a(p) = p, for p prime.