|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
|
|
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..]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|