A138758 - OEIS

A138758

Index of A001203(n) (continued fraction for Pi) in A000040 (primes), or 0 if A001203(n) is not prime.

2, 4, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 2, 6, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 2, 3, 0, 0, 0, 0, 0, 4, 0, 1, 2, 4, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 3, 1, 1, 2, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 2, 0, 1, 0, 0, 0, 1, 3, 0, 0, 1

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OFFSET

1,1

LINKS

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

FORMULA

a(n) = A000720(A001203(n)) * A010051(A001203(n)).

EXAMPLE

This sequence starts 2,4,0,0,... since the 1st and 2nd terms of the continued fraction expansion of Pi, A001203 = (3, 7, 15, 1, ...) are the 2nd resp. 4th primes, while the next two terms are not primes.

PROG

(PARI) default(realprecision, 1000); t=contfrac(Pi); vector(#t, i, isprime(t[i])*primepi(t[i]))

CROSSREFS

Cf. A001203, A138757, A138759, A005042.

Sequence in context: A166926 A266296 A028573 * A107501 A126732 A371648

Adjacent sequences: A138755 A138756 A138757 * A138759 A138760 A138761

KEYWORD

nonn

AUTHOR

M. F. Hasler, Mar 31 2008

STATUS

approved