A153031 Positions of prime digits of Pi.

1, 5, 7, 9, 10, 11, 14, 16, 17, 18, 22, 25, 26, 28, 29, 30, 32, 34, 40, 44, 47, 48, 49, 52, 54, 57, 62, 64, 65, 67, 74, 77, 84, 87, 90, 91, 92, 94, 97, 100, 103, 110, 112, 113, 115, 116, 121, 124, 131, 132, 134, 136, 137, 138, 140, 141, 142, 143, 144, 150, 157, 159, 161

Offset: 1

Author

Julio Cesar de la Yncera, Dec 17 2008

Keywords

• nonn
• base

Links

• Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000796.

Programs

Mathematica

Flatten[Position[ Map[If[PrimeQ[ # ], "*", # ] &, RealDigits[ N[Pi, 100]][[1]]], "*"]]
Select[ Range@ 166, PrimeQ[ RealDigits[Pi, 10, 166][[1, # ]]] &] (* Robert G. Wilson v, Dec 21 2008 *)
Flatten[Position[RealDigits[Pi,10,200][[1]],?PrimeQ]] (* _Harvey P. Dale, Mar 22 2015 *)

PARI

\p 1000
p=Vec(Str(Pi/10)); for(n=1, #p-9, if(isprime(eval(p[n+2])), print1(n", "))) \\ Jens Kruse Andersen, Jul 23 2014

Formula

a(n) = A073303(n) + 1. - Michel Marcus, May 29 2014

Extensions

More concise Mathematica coding added and sequence extended by Robert G. Wilson v, Dec 21 2008