OFFSET
1,1
COMMENTS
Subsequence of A007774.
A033850 is a subsequence.
Subsequence of A195106. - Reinhard Zumkeller, Sep 13 2011
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..250
Eric Weisstein's World of Mathematics, Cousin Primes.
FORMULA
EXAMPLE
MATHEMATICA
dpf2Q[n_]:=Module[{fi=FactorInteger[n][[;; , 1]]}, Length[fi]==2&&fi[[2]]-fi[[1]]==4]; Select[Range[22000], dpf2Q] (* Harvey P. Dale, Mar 18 2023 *)
PROG
(Haskell)
a143203 n = a143203_list !! (n-1)
a143203_list = filter f [1, 3..] where
f x = length pfs == 2 && last pfs - head pfs == 4 where
pfs = a027748_row x
-- Reinhard Zumkeller, Sep 13 2011
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Reinhard Zumkeller, Aug 12 2008
STATUS
approved