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 A133996 a(n) = the smallest positive integer with exactly n positive "non-isolated divisors". A divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n. 3
 2, 6, 12, 30, 60, 90, 180, 360, 630, 420, 840, 1680, 4200, 1260, 2520, 3780, 7560, 15120, 13860, 36960, 49140, 27720, 32760, 65520, 83160, 98280, 196560, 314160, 277200, 491400, 526680, 471240, 360360, 1164240, 942480, 720720, 1081080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Ray Chandler, Table of n, a(n) for n=2..85 MATHEMATICA With[{s = KeySort@ PositionIndex@ Table[1 + Count[Rest@ Divisors@ n, _?(AnyTrue[# + {-1, 1}, Divisible[n, #] &] &)], {n, 1200000}]}, Function[t, TakeWhile[#, # > 0 &] &@ Rest@ ReplacePart[t, Map[# -> Lookup[s, #][[1]] &, Keys@ s]]]@ ConstantArray[0, Last@ Keys@ s]] (* Michael De Vlieger, Oct 11 2017 *) CROSSREFS Cf. A133997, A132747. Sequence in context: A179674 A038199 A056267 * A284573 A080742 A005417 Adjacent sequences:  A133993 A133994 A133995 * A133997 A133998 A133999 KEYWORD nonn AUTHOR Leroy Quet, Oct 01 2007 EXTENSIONS Extended by Ray Chandler, Jun 24 2008 STATUS approved

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Last modified August 13 00:27 EDT 2020. Contains 336441 sequences. (Running on oeis4.)