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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
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
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.)