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A112733
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Smallest prime of the form 1 followed by n copies of k.
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1
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11, 199, 1777, 137373737, 199999, 1131313131313, 19999999, 14747474747474747, 1777777777, 113131313131313131313, 11111111111111111111111, 1171717171717171717171717, 17777777777777, 18787878787878787878787878787, 1333333333333333
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(3) = 1777 1 followed by three copies of 7. 1111 and 1333 are composite.
a(4) = 137373737 is 1 followed by four copies of 37.
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PROG
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(PARI) makestring(n, k) = {d = digits(k); v = vector(n*#d+1); v[1] = 1; ipos = 2; for (i=1, n, for (j=1, #d, v[ipos] = d[j]; ipos++; ); ); s = ""; for (i=1, #v, s = concat(s, v[i])); eval(s); }
a(n) = {k = 1; while (! isprime(v=makestring(n, k)), k++); v; } \\ Michel Marcus, Nov 12 2013
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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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EXTENSIONS
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STATUS
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approved
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