A156899 - OEIS

A156899

a(n) = the largest prime power <= the n-th positive squarefree integer.

1, 2, 3, 5, 5, 7, 9, 11, 13, 13, 13, 17, 19, 19, 19, 23, 25, 29, 29, 31, 32, 32, 32, 37, 37, 37, 41, 41, 43, 43, 47, 49, 53, 53, 53, 53, 59, 61, 61, 64, 64, 67, 67, 67, 71, 73, 73, 73, 73, 79, 81, 83, 83, 83, 83, 89, 89, 89, 89, 89, 97, 101, 101, 103, 103, 103, 107, 109, 109

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OFFSET

1,2

COMMENTS

The first positive squarefree integer is considered to be 1 here.

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

MATHEMATICA

Block[{nn = 110, s}, s = Select[Range[nn], SquareFreeQ]; Map[If[# == 1, 1, SelectFirst[# - Range[0, # - 1], PrimePowerQ]] &, s]] (* Michael De Vlieger, Oct 30 2017 *)

CROSSREFS

Cf. A081217, A156898, A156900, A005117, A000961.

Sequence in context: A092391 A187322 A335429 * A347737 A332286 A357250

Adjacent sequences: A156896 A156897 A156898 * A156900 A156901 A156902

KEYWORD

nonn

AUTHOR

Leroy Quet, Feb 17 2009

EXTENSIONS

Extended by Ray Chandler, Jun 19 2009

STATUS

approved