primes in pi: 1, 2, 6, 38, 16208, 47577, 78073, ...

[N. J. A. Sloane]

Richard Guy said:
> It would be more natural (??) to do this in base 2.
> 
> So here are two new(?) sequences for people to
> check and extend:
> 
> The first
>           2,  8,    14,    18,   ...
> 
> digits in the binary representation of pi form the
> primes
>           3, 401, 25667, 410687, ...
> 
> in decimal notation.
  
Me:

The binary expansion of Pi is A004601:
1,1,0,0,1,0,0,1,0,0,0,0,1,1,1,1,1,1,0,1,1,0,1,0,1,0,1,0,...

Converting first n bits to an integer gives A068425:
1,3,6,12,25,50,100,201,402,804,1608,3216,...

The primes here are A117721:
3,6588397,1686629713,26986075409,16703571626015105435307505830654230989, ...

and they occur for these values of n (A065987):
2,23,31,35,124,323,2787,5717,6506 (and that's all I have)
The latter sequence was computed by Bob Wilson.

Eric, can you extend it?

Richard, I seem to disagree with your results, but perhaps
I misunderstood your message?

Neil