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 A232450 Largest prime factor of the Belphegor number B(n) = (10^(n+3) + 666)*10^(n+1) + 1. 4
 16661, 1103, 1417831, 1143749, 14282381, 11699423, 1950071, 7503425119, 3837692792387, 145857793, 76607717987, 1755833757671518620617, 17416012536871141, 1000000000000066600000000000001, 16540928199996367, 744657085412168192717253704669 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS The Belphegor numbers (A232449), though not often prime themselves (see A232448), tend to contain very large prime factors and are therefore hard to factorize. LINKS Stanislav Sykora and Amiram Eldar, Table of n, a(n) for n = 0..64 (terms 0..44 from Stanislav Sykora) Clifford A. Pickover, Belphegor's Prime: 1000000000000066600000000000001 Wikipedia, Belphegor's prime MATHEMATICA Table[FactorInteger[(10^(n + 3) + 666)*10^(n + 1) + 1][[-1, 1]], {n, 20}] (* T. D. Noe, Nov 25 2013 *) PROG (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])) CROSSREFS Cf. A232448 (indices of Belphegor primes), A232449 (Belphegor numbers). Sequence in context: A170788 A057329 A349773 * A317179 A196023 A108843 Adjacent sequences: A232447 A232448 A232449 * A232451 A232452 A232453 KEYWORD nonn AUTHOR Stanislav Sykora, Nov 24 2013 STATUS approved

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Last modified November 30 21:14 EST 2023. Contains 367462 sequences. (Running on oeis4.)