%I
%S 2,3,5,7,2,2,3,3,5,5,7,7,7,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,
%T 3,3,3,3,3,3,3,3,3,3,3,5,5,5,5,5,5,5,5,5,5,5,5,5,5,7,7,7,7,7,7,7,7,7,
%U 7,7,7,7,7,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
%N Scan primes, write down initial digit if it is a prime.
%o (PARI) firstpr(n) = { forprime(x=2,n, fd = eval(mid(Str(x),1,1)); if(isprime(fd),print1(fd",")) ) } \ Get a substring of length n from string str starting at position s in str. mid(str,s,n) = { v =""; tmp = Vec(str); ln=length(tmp); for(x=s,s+n1, v=concat(v,tmp[x]); ); return(v) }
%Y Cf. A077648.
%K base,nonn
%O 2,1
%A _Cino Hilliard_, Apr 25 2004
