A073488 Squarefree numbers having exactly two prime gaps.

110, 130, 170, 182, 190, 230, 238, 266, 273, 290, 310, 322, 357, 370, 374, 399, 406, 410, 418, 430, 434, 470, 483, 494, 506, 518, 530, 546, 561, 574, 590, 598, 602, 609, 610, 627, 638, 651, 658, 670, 682, 710, 714, 730, 741, 742, 754, 759, 777, 782, 790

Offset: 1

Author

Reinhard Zumkeller, Aug 03 2002

Keywords

• nonn

Examples

			1430 is a term, as 1430 = 2*5*11*13 with two gaps: between 2 and 5 and between 5 and 11.
		

Links

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

Crossrefs

Cf. A005117, A073486, A073487, A073489, A073494.

Programs

Mathematica

q[n_] := SequenceCount[FactorInteger[n][[;; , 1]], {p1_, p2_} /; p2 != NextPrime[p1], Overlaps -> True] == 2; Select[Range[800], SquareFreeQ[#] && q[#] &] (* Amiram Eldar, Apr 10 2021 *)

Formula

A073484(a(n)) = 2.