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A069187
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Numbers n such that core(n)=ceil(sqrt(n)) where core(x) is the squarefree part of x (the smallest integer such that x*core(x) is a square).
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2
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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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
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MATHEMATICA
| core[n_] := Times @@ Apply[ Power, {#[[1]], Mod[#[[2]], 2]}& /@ FactorInteger[n], {1}]; Select[Range[500000], core[#] == Ceiling[Sqrt[#]]&] (* From J.F.Alcover, Jul 26 2011 *)
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CROSSREFS
| Sequence in context: A098077 A063663 A071253 * A033840 A086755 A107483
Adjacent sequences: A069184 A069185 A069186 * A069188 A069189 A069190
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 14 2002
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