

A069187


Numbers n such that core(n) = ceiling(sqrt(n)) where core(x) is the squarefree part of x (the smallest integer such that x*core(x) is a square).


2



1, 2, 20, 90, 272, 650, 1332, 4160, 6642, 10100, 14762, 20880, 28730, 38612, 50850, 65792, 83810, 130682, 160400, 194922, 234740, 280370, 332352, 391250, 457652
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OFFSET

1,2


COMMENTS

Conjecture: sequence is A071253 minus those entries of A071253 that have their index in A049532, i.e., a(n) is of form n^2*(n^2+1) for all n not in A049532.  Ralf Stephan, Aug 18 2004


LINKS

Table of n, a(n) for n=1..25.


MATHEMATICA

core[n_] := Times @@ Apply[ Power, {#[[1]], Mod[#[[2]], 2]}& /@ FactorInteger[n], {1}]; Select[Range[500000], core[#] == Ceiling[Sqrt[#]]&] (* JeanFrançois Alcover, Jul 26 2011 *)


CROSSREFS

Sequence in context: A279264 A063663 A071253 * A328510 A033840 A086755
Adjacent sequences: A069184 A069185 A069186 * A069188 A069189 A069190


KEYWORD

easy,nonn


AUTHOR

Benoit Cloitre, Apr 14 2002


STATUS

approved



