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

Author

Jani Melik, Oct 09 2004

Keywords

• nonn

Examples

			a(1)=2 is oblong and squarefree.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A002378 or A229882 with A030059.

Cf. A005117.

Programs

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 *)