A074908 - OEIS

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

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OFFSET

0,1

LINKS

Table of n, a(n) for n=0..104.

EXAMPLE

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.

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);

CROSSREFS

Cf. A061265, A061399.

Sequence in context: A226774 A037968 A303378 * A307713 A328680 A256707

Adjacent sequences: A074905 A074906 A074907 * A074909 A074910 A074911

KEYWORD

nonn

AUTHOR

Jani Melik, Sep 30 2002

STATUS

approved