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A114434
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To obtain a(n), write the n-th composite number as a product of primes, add 1 to each prime and multiply.
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2
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9, 12, 27, 16, 18, 36, 24, 24, 81, 48, 54, 32, 36, 108, 36, 42, 64, 72, 72, 243, 48, 54, 48, 144, 60, 56, 162, 96, 108, 96, 72, 324, 64, 108, 72, 126, 192, 72, 216, 80, 90, 216, 96, 128, 729, 84, 144, 162, 96, 144, 432, 114, 144, 180, 96, 168, 486, 256
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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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MAPLE
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b:= proc(n) option remember; local k;
for k from 1+`if`(n=1, 3, b(n-1))
while isprime(k) do od; k
end:
a:= n-> mul((i[1]+1)^i[2], i=ifactors(b(n))[2]):
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MATHEMATICA
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f[n_] := Module[{p, e},
Product[{p, e} = pe; (p+1)^e, {pe, FactorInteger[n]}]];
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PROG
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(PARI) lista(nn) = {forcomposite(c=2, nn, f = factor(c); print1(prod(i=1, #f~, (f[i, 1]+1)^f[i, 2]), ", "); ); } \\ Michel Marcus, Jun 26 2013
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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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