A047846 Number of successive odd nonprimes (A014076).

1, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 1, 2, 1, 2, 3, 1, 1, 1, 6, 1, 2, 4, 2, 2, 1, 2, 2, 4, 1, 5, 5, 1, 1, 2, 4, 2, 2, 2, 2, 1, 4, 6, 1, 1, 6, 2, 4, 1, 2, 3, 2, 2, 1, 2, 3, 1, 3, 4, 4, 2, 1, 2, 3, 1, 1, 5, 3, 1, 3, 1, 2, 5, 8, 2, 4, 2, 2, 2, 4, 2, 2, 2, 2, 1, 5

Offset

1,5

Comments

Beginning with a(2), length of n-th run of identical numbers in A160522. [Kyle Stern, Jun 19 2009]

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Formula

a(n+1) = A196277(n+1) - A196277(n). [Reinhard Zumkeller, Sep 30 2011]

Mathematica

Length /@ Split[Select[Range[1, 629, 2], PrimeOmega[#] != 1 &], #2 - #1 <= 2 &] (* Jayanta Basu, Aug 11 2013 *)
(* Alternative: *)
Length/@Select[Split[Table[If[PrimeQ[n], 0, 1], {n, 1, 701, 2}]], #[[1]]==1&] (* Harvey P. Dale, Oct 10 2023 *)

Prog

(Haskell)
a047846 n = a047846_list !! (n-1)
a047846_list = 1 : zipWith (-) (tail a196277_list) a196277_list
-- Reinhard Zumkeller, Sep 30 2011

Crossrefs

Length of n-th run in A014076.

Cf. A160522.

Sequence in context: A102715 A254687 A182590 * A345699 A212632 A359477

Adjacent sequences: A047843 A047844 A047845 * A047847 A047848 A047849

Keyword

easy,nonn

Author

Enoch Haga

Extensions

a(51) and a(84) corrected by Reinhard Zumkeller, Sep 30 2011

Status

approved