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A089993
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Penultimate prime divisor of numbers that are not powers of primes (A024619).
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2
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2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 3, 3, 2, 5, 2, 2, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 3, 2, 3, 5, 3, 2, 3, 5, 2, 2, 3, 2, 7, 3, 2, 2, 3, 5, 2, 3, 2, 3, 7, 2, 3, 2, 5, 2, 2, 3, 2, 3, 2, 5, 2, 2, 5, 3, 2, 3, 5, 2, 3, 2, 7, 3, 2, 3, 2, 3, 3, 5, 3, 7, 2, 3, 2, 3, 5, 3, 2, 11, 2, 5, 2, 3, 2, 3, 2, 3, 7, 5
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OFFSET
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1,1
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LINKS
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FORMULA
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MATHEMATICA
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Select[Table[If[Length[(f = FactorInteger[n])] > 1, f[[-2, 1]], 1], {n, 1, 150}], # > 1 &]
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PROG
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(PARI) f(n) = a=factor(n); v=a[, 1]; ln=length(v); if(ln>1, return(v[ln-1]));
g(m) = for(x=2, m, if(f(x)>0, print1(f(x)", ")))
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CROSSREFS
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KEYWORD
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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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