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

Author

Enoch Haga

Keywords

• easy
• nonn

Comments

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

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

Links

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

Crossrefs

Length of n-th run in A014076.

Cf. A160522.

Programs

Haskell

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

Mathematica

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

Extensions

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