A093338 Scan primes, write down initial digit if it is a prime.

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, 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, 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

Offset

2,1

Links

Table of n, a(n) for n=2..106.

Prog

(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+n-1, v=concat(v, tmp[x]); ); return(v) }

Crossrefs

Cf. A077648.

Sequence in context: A032759 A142711 A357096 * A229875 A230199 A275542

Adjacent sequences: A093335 A093336 A093337 * A093339 A093340 A093341

Keyword

base,nonn

Author

Cino Hilliard, Apr 25 2004

Status

approved