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%I #7 Apr 10 2021 22:23:44
%S 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,
%T 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,
%U 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
%N Index of A001203(n) (continued fraction for Pi) in A000040 (primes), or 0 if A001203(n) is not prime.
%F a(n) = A000720(A001203(n)) * A010051(A001203(n)).
%e 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.
%o (PARI) default(realprecision,1000); t=contfrac(Pi); vector(#t,i,isprime(t[i])*primepi(t[i]))
%Y Cf. A001203, A138757, A138759, A005042.
%K nonn
%O 1,1
%A _M. F. Hasler_, Mar 31 2008
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