OFFSET
1,1
COMMENTS
In other words, take the decimal expansion of Pi, drop any digits greater than 1, omit the decimal point and look for prefixes in the resulting string which form base-2 primes.
Numbers k such that A065830(k) is prime.
EXAMPLE
The first a(3)=10 binary digits of Pi are 1101110001_2 which is prime 881_10.
MATHEMATICA
p = First[ RealDigits[ Pi, 10, 10^5]]; p = p[[ Select[ Range[10^5], p[[ # ]] == 0 || p[[ # ]] == 1 & ]]]; Do[ If[ PrimeQ[ FromDigits[ Take[p, n], 2]], Print[n]], {n, 1, Length[p] } ]
CROSSREFS
KEYWORD
nonn,base,hard,more
AUTHOR
Patrick De Geest, Nov 24 2001
EXTENSIONS
More terms from Robert G. Wilson v, Nov 30 2001
a(15)-a(16) from Chai Wah Wu, Apr 06 2020
a(17) from Michael S. Branicky, Sep 25 2024
STATUS
approved