

A138759


Indices for which A001203 (continued fraction for Pi) is prime.


4



1, 2, 9, 11, 14, 17, 18, 19, 20, 23, 27, 28, 31, 36, 37, 39, 40, 46, 48, 49, 50, 52, 59, 65, 70, 71, 72, 73, 75, 85, 86, 90, 93, 95, 97, 101, 102, 105, 106, 109, 110, 111, 118, 120, 122, 123, 124, 127, 128, 131, 132, 133, 140, 142, 145, 146, 151, 152, 153, 155, 159
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..61.


FORMULA

k is in A138759 <=> A001203(k) is in A000040


EXAMPLE

This sequence starts 1,2,9,11,... since the first, 2nd, 9th, 11th...
term of sequence A001203 = (3, 7, 15, 1, 292, 1, 1, 1, 2, ...) are primes.


MATHEMATICA

Position[ContinuedFraction[Pi, 200], _?PrimeQ]//Flatten(* Harvey P. Dale, Aug 07 2019 *)


PROG

(PARI) default(realprecision, 1000); t=contfrac(Pi); for( k=1, #t, isprime(t[k]) & print1(k", "))


CROSSREFS

Cf. A001203, A005042, A107892, A138758.
Sequence in context: A073634 A065554 A034042 * A345925 A098934 A237877
Adjacent sequences: A138756 A138757 A138758 * A138760 A138761 A138762


KEYWORD

nonn


AUTHOR

M. F. Hasler, Mar 31 2008


STATUS

approved



