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A093339
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Middle digits of primes with an odd number of digits.
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3
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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
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2,1
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LINKS
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MATHEMATICA
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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 *)
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PROG
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(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) }
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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