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.

Showing 1-3 of 3 results.

A074592 Smallest prime factors of numbers that are not prime powers.

Original entry on oeis.org

2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 2, 2, 3, 5, 2, 2, 3, 2, 2, 2, 3, 2, 7, 2, 2, 2, 2, 5, 2, 3, 2, 2, 7, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 7, 2, 2, 3, 2, 2, 3, 2, 2, 7, 2, 3, 2, 2, 2, 3, 2, 11, 2, 5, 2, 3, 2, 2, 2, 3, 2
Offset: 1

Views

Author

Reinhard Zumkeller, Aug 25 2002

Keywords

Links

Crossrefs

Cf. A006549, A020639, A024619, A074593, A074594, A074595.

Programs

  • Mathematica
    s[n_] := Module[{f = FactorInteger[n]}, If[Length[f] > 1, f[[1, 1]], Nothing]]; Array[s, 200] (* Amiram Eldar, Oct 10 2024 *)

Formula

a(n) = A020639(A024619(n)).
a(n) > 2 iff n+1 and n+2 are prime powers (A006549).

A074594 Number of distinct prime factors of numbers that are not prime powers.

Original entry on oeis.org

2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 3, 3, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2
Offset: 1

Views

Author

Reinhard Zumkeller, Aug 25 2002

Keywords

Links

Crossrefs

Cf. A074595, A074592, A074593.

Programs

  • Mathematica
    PrimeNu/@Select[Range[2,300],!PrimePowerQ[#]&] (* Harvey P. Dale, Nov 18 2018 *)

Formula

a(n) = A001221(A024619(n)).

A074595 Number of prime factors of numbers that are not prime powers (with multiplicity).

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, Aug 25 2002

Keywords

Links

Crossrefs

Cf. A001222, A024619, A074594, A074592, A074593.

Programs

  • Mathematica
    s[n_] := Module[{f = FactorInteger[n]}, If[Length[f] > 1, Total[f[[;; , 2]]], Nothing]]; Array[s, 200] (* Amiram Eldar, Oct 10 2024 *)

Formula

a(n) = A001222(A024619(n)).
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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