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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 23 20:31 EDT 2021. Contains 348215 sequences. (Running on oeis4.)