A102300 Number of distinct prime divisors of n where n and n+1 are composite or twin composite numbers.

1, 1, 2, 2, 2, 2, 2, 1, 2, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 3, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 1, 1, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 3, 3, 1, 3, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2

Offset

1,3

Links

Table of n, a(n) for n=1..105.

Example

For n=8 n+1=9 a twin composite pair. 8=2^3 has 1 distinct divisor, 2.

Prog

(PARI) f2(n) = for(x=1, n, y=composite(x); if(!isprime(y+1), print1(omega(y)", "))) composite(n) =\The n-th composite number. 1 is def as not prime nor composite. { local(c, x); c=1; x=1; while(c <= n, x++; if(!isprime(x), c++); ); return(x) }

Crossrefs

Sequence in context: A083534 A174664 A027386 * A359511 A202146 A087010

Adjacent sequences: A102297 A102298 A102299 * A102301 A102302 A102303

Keyword

easy,nonn

Author

Cino Hilliard, Feb 19 2005

Status

approved