A111406 a(n) = f(f(n+1)) - f(f(n)), where f(m) = pi(m) = A000720(m), with f(0) = 0.

0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 0

Author

N. J. A. Sloane, Nov 12 2005

Keywords

• nonn

Comments

Right-shifted sequence is characteristic function of prime-indexed primes (A006450). - Franklin T. Adams-Watters, Nov 17 2006

Links

• Antti Karttunen, Table of n, a(n) for n = 0..65557
• Index entries for characteristic functions

Crossrefs

Cf. A000720, A006450.

Programs

PARI

A111406(n) = (primepi(primepi(n+1)) - primepi(primepi(n))); \\ Antti Karttunen, Dec 07 2017

Extensions

Missing right parenthesis added to the formula and case f(0) clarified by Antti Karttunen, Dec 07 2017