A243290 The index of the greatest prime dividing the n-th squarefree number: a(n) = A061395(A005117(n)).

0, 1, 2, 3, 2, 4, 3, 5, 6, 4, 3, 7, 8, 4, 5, 9, 6, 10, 3, 11, 5, 7, 4, 12, 8, 6, 13, 4, 14, 9, 15, 7, 16, 5, 8, 10, 17, 18, 11, 6, 5, 19, 9, 4, 20, 21, 12, 5, 6, 22, 13, 23, 7, 14, 10, 24, 6, 11, 15, 8, 25, 26, 7, 27, 4, 16, 28, 29, 5, 12

Offset: 1

Author

Antti Karttunen, Jun 03 2014

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005117, A006530, A061395, A049084, A048672, A070939, A243289.

Programs

Mathematica

Table[PrimePi[FactorInteger[k][[-1, 1]]], {k, Select[Range[120], SquareFreeQ]}] (* Amiram Eldar, Mar 04 2024 *)

Formula

a(n) = A061395(A005117(n)) = A049084(A006530(A005117(n))).

For all n>1, a(n) = A070939(A048672(n)).