A074908 Number of integers with an odd number of distinct primes (for which mu(n)=-1) between two consecutive primes prime(n) and prime(n+1).

2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 3, 3, 2, 3, 2, 2, 2, 2, 3, 3, 2, 3, 3, 3, 2, 3, 2, 2, 3, 2, 3, 3, 3, 2, 5, 2, 3, 2, 2, 3, 2, 2, 4, 3, 2, 3, 3, 3, 3, 2, 3, 2, 3, 5, 2, 3, 2, 2, 4, 2, 3, 2, 2, 4, 3, 3, 3, 2, 3, 2, 3, 4, 4, 2, 5, 2, 5, 3, 2, 3, 2, 2, 3, 4, 3, 2, 4, 2, 3, 3, 2, 4, 2, 3, 3, 2, 2, 3

Offset: 1

Author

Jani Melik, Sep 30 2002

Keywords

• nonn

Examples

			Between 7919 and 7927 the 5 numbers which have an odd number of distinct primes are as follows: {7919,7922,7923,7926,7927}, so a(1000)=5.
		

Crossrefs

Cf. A061265, A061399.

Programs

Maple

readlib(issqr): lstmp := proc(n) local t1,i; t1 := 0; for i from ithprime(n) to ithprime(n+1) do if (issqrfree(i) = 'true' and mobius(i)=-1) then t1 := t1+1; fi; od; t1; end: lstmp(200);

Extensions

Offset corrected by Sean A. Irvine, Feb 01 2025