login
A077477
Least positive integers not excluded by the rule that if n is present then 2n+1 and 3n+1 are not allowed.
6
1, 2, 6, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 22, 24, 26, 27, 30, 32, 35, 36, 38, 39, 40, 42, 44, 47, 48, 50, 51, 52, 54, 56, 57, 58, 59, 60, 62, 63, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 83, 84, 86, 87, 88, 90, 92, 93, 94, 96
OFFSET
1,2
COMMENTS
What is the limit of a(n)/n?
With 10000 terms, one gets a(n)/n -> 1.63317... - Jean-François Alcover Dec 11 2012
LINKS
EXAMPLE
a(5)=9 since 9 is not equal to 2*a(k)+1 nor 3*a(k)+1 for 1<=k<5; and since 9 is allowed to be present, then 19(=2*9+1) and 28(=3*9+1) are to be excluded.
MATHEMATICA
s = {1}; Do[u = Union[s, 2s + 1, 3s + 1]; c = Complement[Range[u // Last], u] // First; AppendTo[s, c], {10000}]; s (* Jean-François Alcover, Dec 11 2012 *)
PROG
(Haskell)
import Data.List (delete)
a077477 n = a077477_list !! (n-1)
a077477_list = f [1..] where
f (x:xs) = x : f (delete (2*x + 1) $ delete (3*x + 1) xs)
-- Reinhard Zumkeller, Sep 14 2011
CROSSREFS
Cf. A002977.
Sequence in context: A003610 A201776 A206476 * A095879 A342751 A120736
KEYWORD
easy,nice,nonn
AUTHOR
Paul D. Hanna, Nov 08 2002
STATUS
approved