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 A073247 Squarefree numbers n such that n-1 and n+1 are not squarefree. 10
 17, 19, 26, 51, 53, 55, 89, 91, 97, 127, 149, 151, 161, 163, 170, 197, 199, 233, 235, 241, 249, 251, 269, 271, 293, 295, 305, 307, 337, 339, 341, 349, 362, 377, 379, 413, 415, 449, 451, 485, 487, 489, 491, 521, 523, 530, 551, 557, 559, 577, 579, 593, 595 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Probably 11*n < a(n) < 12*n for n > 189. - Charles R Greathouse IV, Nov 05 2017 LINKS Christopher E. Thompson, Table of n, a(n) for n = 1..10000 MAPLE sf:= select(numtheory:-issqrfree, [\$1..1000]): map(t -> `if`(sf[t-1]=sf[t]-1 or sf[t+1]=sf[t]+1, NULL, sf[t]), [\$2..nops(sf)-1]); # Robert Israel, Feb 01 2016 MATHEMATICA Reap[For[n = 0, n <= 1000, n++, If[SquareFreeQ[n] && !SquareFreeQ[n-1] && !SquareFreeQ[n+1], Sow[n]]]][[2, 1]] (* Jean-François Alcover, Feb 26 2019 *) PROG (PARI) is(n)=!issquarefree(n-1) && issquarefree(n) && !issquarefree(n+1) \\ Charles R Greathouse IV, Nov 05 2017 CROSSREFS Cf. A005117, A073249, A073248, A007675. Cf. A268331, A268332, A268333, A268334 (squarefrees isolated by more than 2, 3, etc.). Sequence in context: A249566 A205646 A281192 * A133347 A096990 A175384 Adjacent sequences: A073244 A073245 A073246 * A073248 A073249 A073250 KEYWORD nonn AUTHOR Reinhard Zumkeller, Jul 22 2002 STATUS approved

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Last modified March 29 18:41 EDT 2023. Contains 361599 sequences. (Running on oeis4.)