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A073495
Numbers having exactly three prime gaps in their factorization.
14
1870, 2090, 2470, 2530, 2990, 3190, 3410, 3458, 3740, 3770, 3910, 4030, 4070, 4180, 4186, 4510, 4730, 4810, 4930, 4940, 5060, 5170, 5187, 5270, 5278, 5330, 5474, 5510, 5590, 5642, 5830, 5890, 5980, 6110, 6279, 6290, 6380, 6490, 6710, 6734, 6820, 6890
OFFSET
1,1
LINKS
FORMULA
A073490(a(n)) = 3.
EXAMPLE
1870 is a term, as 1870 = 2*5*11*17 with three gaps: between 2 and 5, between 5 and 11 and between 11 and 17.
MATHEMATICA
q[n_] := SequenceCount[FactorInteger[n][[;; , 1]], {p1_, p2_} /; p2 != NextPrime[p1], Overlaps -> True] == 3; Select[Range[7000], q] (* Amiram Eldar, Apr 10 2021*)
PROG
(Haskell)
a073495 n = a073495_list !! (n-1)
a073495_list = filter ((== 3) . a073490) [1..]
-- Reinhard Zumkeller, Dec 20 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Aug 03 2002
STATUS
approved