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 A193873 Smallest product of three distinct primes of the form n*k+1. 3
 30, 105, 1729, 1105, 13981, 1729, 88537, 50881, 51319, 13981, 137149, 29341, 548497, 88537, 285541, 186337, 3372529, 51319, 18326641, 252601, 1152271, 137149, 1809641, 1366633, 3828001, 548497, 4814857, 645569, 4797703, 285541, 79230049, 4811297 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Note that the Hardy-Ramanujan is the first and the smallest repeated number: a(3)=a(6)=1729. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 EXAMPLE a(1) = 2*3*5 = 30 a(2) = 3*5*7 = 105 a(3) = 7*13*19 = 1729 a(4) = 5*13*17 = 1105 a(5) = 11*31*41 = 13981 PROG (PARI) a(n)=my(p, q, k=1); while(!isprime(k+=n), ); p=k; while(!isprime(k+=n), ); q=k; while(!isprime(k+=n), ); p*q*k \\ Charles R Greathouse IV, Sep 03 2011 CROSSREFS Cf. A001235, A077316, A092609, A121940, A154729, A193869. Sequence in context: A257891 A158445 A046301 * A266955 A205836 A043466 Adjacent sequences: A193870 A193871 A193872 * A193874 A193875 A193876 KEYWORD nonn,easy AUTHOR Omar E. Pol, Sep 02 2011 STATUS approved

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Last modified December 2 08:36 EST 2022. Contains 358493 sequences. (Running on oeis4.)