A176451 Number of primes between two consecutive nonprimes in A037143.

2, 1, 1, 0, 2, 0, 2, 0, 1, 0, 2, 0, 0, 1, 0, 2, 1, 0, 1, 0, 0, 2, 0, 1, 2, 0, 1, 1, 0, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0, 0, 0, 0, 1, 1, 0, 2, 0, 0, 0, 0, 2, 1, 0, 0, 1, 1, 1, 0, 2, 0, 0, 2, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 3, 0, 2, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 18 2010

Keywords

• nonn
• easy

Comments

2 together with the number of primes between successive semiprimes.

Examples

			a(1) = 2 because A037143(1) = 1 (nonprime) < A037143(2) = 2 (prime) < A037143(3) = 3 (prime) < A037143(4) = 4 (nonprime).
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A037143, A088700.

Programs

Mathematica

Join[{2}, -1 + Differences[Position[Select[PrimeOmega[Range[400]], # < 3 &], 2] // Flatten]] (* Amiram Eldar, Sep 07 2024 *)

Formula

a(n) = A088700(n-1) for n >= 2.