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A232450
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Largest prime factor of the Belphegor number B(n) = (10^(n+3) + 666)*10^(n+1) + 1.
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4
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16661, 1103, 1417831, 1143749, 14282381, 11699423, 1950071, 7503425119, 3837692792387, 145857793, 76607717987, 1755833757671518620617, 17416012536871141, 1000000000000066600000000000001, 16540928199996367, 744657085412168192717253704669
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OFFSET
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0,1
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COMMENTS
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The Belphegor numbers (A232449), though not often prime themselves (see A232448), tend to contain very large prime factors and are therefore hard to factorize.
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LINKS
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MATHEMATICA
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Table[FactorInteger[(10^(n + 3) + 666)*10^(n + 1) + 1][[-1, 1]], {n, 20}] (* T. D. Noe, Nov 25 2013 *)
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PROG
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(PARI) default(factor_proven, 1);
Belphegor(k)=(10^(k+3)+666)*10^(k+1)+1;
LargestPrimeFactor(k)={local(f); f=factor(k); return(f[#f[, 1], 1])};
nmax=40; v=vector(nmax);
for (n=0, #v-1, v[n+1]=LargestPrimeFactor(Belphegor(n)); print(v[n+1]))
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CROSSREFS
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Cf. A232448 (indices of Belphegor primes), A232449 (Belphegor numbers).
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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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