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 A098827 Squarefree oblong (pronic) numbers having an odd number of prime factors. 1
 2, 30, 42, 110, 182, 506, 1406, 2162, 3422, 3782, 4290, 4830, 5402, 6006, 6806, 11130, 11342, 12210, 13110, 16770, 23870, 24806, 27390, 27722, 31862, 33306, 34410, 34782, 37442, 37830, 44310, 49062, 51302, 56406, 60762, 64770, 66822, 68906 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE a(1)=2 is oblong and squarefree. MAPLE ts_nsq_pronic:=proc(n) local i, ans; ans:=[ ]: for i from 1 to n do if (numtheory[mobius]( i*(i+1) ) = -1 ) then ans:=[ op(ans), i*(i+1)]: fi od; RETURN(ans) end: ts_nsq_pronic(500); MATHEMATICA Select[#*(# + 1) & /@ Range[250], MoebiusMu[#1] == -1 &] (* Amiram Eldar, Feb 22 2021 *) CROSSREFS Intersection of A002378 or A229882 with A030059. Cf. A005117. Sequence in context: A127026 A105962 A113695 * A280380 A184238 A285220 Adjacent sequences: A098824 A098825 A098826 * A098828 A098829 A098830 KEYWORD nonn AUTHOR Jani Melik, Oct 09 2004 STATUS approved

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Last modified June 19 16:35 EDT 2024. Contains 373503 sequences. (Running on oeis4.)