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A282795
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Start with n. If n is 1 or a prime, stop. Otherwise, add the prime factors of n (with repetition) to n, and repeat until reaching a prime, when we stop. If no prime is ever reached, a(n) = -1.
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1
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1, 2, 3, 23, 5, 11, 7, 23, 23, 17, 11, 19, 13, 23, 23, 47, 17, 41, 19, 29, 31, 47, 23, 47, 47, 41, 71, 71, 29, 71, 31, 83, 47, 53, 47, 71, 37, 59, 71, 71, 41, 83, 43, 59, 167, 71, 47, 59, 149, 167, 71, 167, 53, 83, 71, 167, 79, 89, 59, 251, 61
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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4 -> 4+2+2 = 8 -> 8+2+2+2 = 14 -> 14+2+7 = 23, prime, so a(4) = 23.
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MAPLE
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local nrec;
nrec := n ;
while not isprime(nrec) and nrec <> 1 do
end do:
nrec ;
end proc:
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MATHEMATICA
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f[n_]:=n+Total[Replace[{a_, b_}->a*b]/@FactorInteger[n]];
a[1]=1; a[n_]:=If[PrimeQ[n], n, Last[NestWhileList[f, n, !PrimeQ[#]&]]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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