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A073494
Numbers having exactly two prime gaps in their factorization.
6
110, 130, 170, 182, 190, 220, 230, 238, 260, 266, 273, 290, 310, 322, 340, 357, 364, 370, 374, 380, 399, 406, 410, 418, 430, 434, 440, 460, 470, 476, 483, 494, 506, 518, 520, 530, 532, 546, 550, 561, 574, 580, 590, 598, 602, 609, 610, 620, 627, 638, 644
OFFSET
1,1
COMMENTS
A073490(a(n)) = 2.
LINKS
EXAMPLE
220 is a term, as 220 = 2*2*5*11 with two gaps: between 2 and 5 and between 5 and 11.
MATHEMATICA
pa[n_, k_] := If[k == NextPrime[n], 0, 1]; Select[Range[645], Total[pa @@@ Partition[First /@ FactorInteger[#], 2, 1]] == 2 &] (* Jayanta Basu, Jul 01 2013 *)
PROG
(Haskell)
a073494 n = a073494_list !! (n-1)
a073494_list = filter ((== 2) . a073490) [1..]
-- Reinhard Zumkeller, Dec 20 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Aug 03 2002
STATUS
approved