A098827 Squarefree oblong (pronic) numbers having an odd number of prime factors.

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

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