%I A060421
%S A060421 1,2,6,38,16208,47577,78073
%N A060421 Numbers n such that the first n digits of the decimal expansion of pi 
               form a prime.
%C A060421 The Brown link states that in 2001 Ed. T. Prothro reported discovering 
               that 16208 gives a probable prime and that Prothro verified that 
               all values for 500 through 16207 digits of pi are composites. - Rick 
               L. Shepherd (rshepherd2(AT)hotmail.com), Sep 10 2002
%C A060421 The corresponding primes are in A005042. - Alexander R. Povolotsky (pevnev(AT)juno.com), 
               Dec 17 2007
%H A060421 K. S. Brown, <a href="http://www.sixfingeredman.net/ref/mathpages-notes/
               kmath184/kmath184.htm">Primes in the Decimal Expansion of Pi</a> 
               [Broken link?]
%H A060421 K. S. Brown, <a href="a060421.htm">Primes in the Decimal Expansion of 
               Pi</a> [Cached copy]
%H A060421 Prime Curios, <a href="http://primes.utm.edu/curios/page.php?short=314159">
               314159</a>
%H A060421 Prime Curios, <a href="http://primes.utm.edu/curios/page.php?number_id=1435">
               31415...36307 (16208-digits)</a>
%H A060421 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               IntegerSequencePrimes.html">Integer Sequence Primes</a>
%H A060421 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Pi-Prime.html">Pi-Prime</a>
%H A060421 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Pi-Prime.html">Pi-Prime</a>
%H A060421 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               IntegerSequencePrimes.html">Integer Sequence Primes</a>
%e A060421 3 is prime, so a(1) = 3; 31 is prime, so a(2) = 31; 314159 is prime, 
               so a(3) = 314159; ...
%t A060421 Do[ If[ PrimeQ[ FromDigits[ RealDigits[ N[ P, n+10], 10, n] [ [1] ] ] 
               ], Print[n] ], {n, 1, 9016} ]
%Y A060421 Cf. A005042, A007523.
%Y A060421 Sequence in context: A005530 A072191 A118324 this_sequence A054970 A120492 
               A028300
%Y A060421 Adjacent sequences: A060418 A060419 A060420 this_sequence A060422 A060423 
               A060424
%K A060421 hard,nonn,base
%O A060421 1,2
%A A060421 Michel ten Voorde (seqfan(AT)tenvoorde.org) Apr 05 2001
%E A060421 a(6) found by Eric Weisstein (eric(AT)weisstein.com), Apr 01 2006
%E A060421 a(7) = 78073 found by Eric Weisstein (eric(AT)weisstein.com), Jul 13 
               2006