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A093338
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Scan primes, write down initial digit if it is a prime.
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0
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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
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internal format)
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OFFSET
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2,1
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LINKS
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PROG
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(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) }
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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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