A093339 Middle digits of primes with an odd number of digits.

2, 3, 5, 7, 0, 0, 0, 0, 1, 2, 3, 3, 3, 4, 5, 5, 6, 6, 7, 7, 8, 9, 9, 9, 9, 1, 2, 2, 2, 3, 3, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 0, 1, 1, 1, 3, 3, 4, 4, 5, 5, 6, 7, 7, 8, 8, 9, 0, 0, 1, 2, 3, 3, 3, 4, 4, 5, 6, 6, 6, 7, 8, 9, 9, 0, 0, 2, 2, 4, 4, 5, 6, 6, 7, 7, 8, 9, 9, 0, 0, 1, 1, 1, 3, 4, 4, 4, 5, 5, 6, 7, 7, 8, 9, 0

Offset: 2

Author

Cino Hilliard, Apr 25 2004

Keywords

• base
• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 2..1000

Crossrefs

Cf. A077648, A007652.

Programs

Mathematica

mdp[n_]:=Module[{idn=IntegerDigits[n],len=IntegerLength[n]},If[EvenQ[len], -1,idn[[(len-1)/2+1]]]]; Select[mdp/@Prime[Range[500]],NonNegative] (* Harvey P. Dale, Feb 26 2012 *)

PARI

midd(n) = { forprime(x=2,n, s = Str(x); ln = length(s); if(ln<2,p=1,p = (ln-1)/2+1); if(ln%2, md = eval(mid(s,p,1)); print1(md",") ) ) } \ 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) }