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.

A188654 Numbers k such that the maximum exponent in its prime factorization does not equal the number of positive exponents (A051903(k) <> A001221(k)).

Original entry on oeis.org

4, 6, 8, 9, 10, 14, 15, 16, 21, 22, 24, 25, 26, 27, 30, 32, 33, 34, 35, 38, 39, 40, 42, 46, 48, 49, 51, 54, 55, 56, 57, 58, 60, 62, 64, 65, 66, 69, 70, 72, 74, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 93, 94, 95, 96, 102, 104, 105, 106, 108, 110, 111
Offset: 1

Views

Author

Reinhard Zumkeller, May 03 2013

Keywords

Crossrefs

Cf. A001221, A212166 (complement), A225230.
Union of A212164 and A212168.

Programs

  • Haskell
    import Data.List (findIndices)
    a188654 n = a188654_list !! (n-1)
    a188654_list = map (+ 1) $ findIndices (/= 0) a225230_list
    
  • Mathematica
    q[n_] := Module[{e = FactorInteger[n][[;;, 2]]}, Max[e] != Length[e]]; q[1] = False; Select[Range[120], q] (* Amiram Eldar, Sep 08 2024 *)
  • PARI
    is(k) = {my(e = factor(k)[, 2]); #e && vecmax(e) != #e;} \\ Amiram Eldar, Sep 08 2024

Formula

A051903(n) <> A001221(n);
A225230(a(n)) <> 0.