A093339 - OEIS

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

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OFFSET

2,1

LINKS

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

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 *)

PROG

(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) }

CROSSREFS

Cf. A077648, A007652.

Sequence in context: A376655 A270517 A124648 * A113566 A020775 A041000

Adjacent sequences: A093336 A093337 A093338 * A093340 A093341 A093342

KEYWORD

base,nonn

AUTHOR

Cino Hilliard, Apr 25 2004

STATUS

approved