



4, 3, 3, 2, 1, 3, 1, 2, 3, 2, 1, 2, 1, 3, 1, 2, 3, 1, 2, 2, 1, 2, 1, 1, 2, 3, 3, 2, 1, 1, 1, 1, 1, 2, 2, 1, 3, 1, 1, 1, 3, 1, 2, 1, 2, 2, 1, 2, 1, 3, 1, 1, 1, 3, 3, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 3, 2, 1, 3, 1, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 3, 1, 1, 1, 2
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

a(n) < 4 for n > 1; a(A196276(a(n)) = 1; a(A196277(a(n)) > 1. [Reinhard Zumkeller, Sep 30 2011]
Lengths of runs of equal terms in A025549. That sequence begins with: 1,1,1,1,3,3,3,45,45,45,..., that is 4 ones, 3 threes, 3 fortyfives, ...  Michel Marcus, Dec 02 2014


LINKS

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


FORMULA

a(n) = (A014076(n+1)A014076(n))/2 = A067970(n)/2.


EXAMPLE

The smallest odd numbers which are not prime are 1, 9, 15, 21, 25, 27,... (sequence A014076).
The gaps between these are: 8, 6, 6, 4, 2,... (sequence A067970), which are of course all even by construction, so it makes sense to divide all of them by 2, which yields this sequence: 4, 3, 3, 2, 1, ...


MATHEMATICA

With[{nn=401}, Differences[Complement[Range[1, nn, 2], Prime[Range[ PrimePi[ nn]]]]]/2] (* Harvey P. Dale, May 06 2012 *)


PROG

(PARI) L=1; forstep(n=3, 299, 2, isprime(n)&next; print1((nL)/2", "); L=n)


CROSSREFS

Cf. A142723 for the decimal value of the associated continued fraction.
Sequence in context: A177038 A019975 A327869 * A073871 A120927 A241180
Adjacent sequences: A196271 A196272 A196273 * A196275 A196276 A196277


KEYWORD

nonn


AUTHOR

M. F. Hasler, Sep 30 2011


EXTENSIONS

More terms from Harvey P. Dale, May 06 2012


STATUS

approved



