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A190664 Least semiprime whose prime factors differ by 2*prime(n). 1

%I

%S 21,55,39,51,203,87,111,123,371,183,335,395,623,267,291,327,1703,635,

%T 411,1043,447,815,1211,543,591,7223,1055,2951,1115,687,771,1883,831,

%U 843,4043,1535,951,1655,1011,1047,12059,1835,2723,1167,1191,1203,4763,1347

%N Least semiprime whose prime factors differ by 2*prime(n).

%F a(n) = A073703(n) * A073704(n).

%e a(5) = 203 because 203 = 7*29, and 29 - 7 = 22 = 2*11 = 2*prime(5).

%t f[n_] := Block[{p=3}, While[! PrimeQ[p+2*Prime[n]], p=NextPrime[p]]; p*(p+2*Prime[n])]; Table[f[n], {n, 1, 60}]

%Y Cf. A073703, A073704.

%K nonn

%O 1,1

%A _Michel Lagneau_, May 16 2011

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Last modified October 16 20:35 EDT 2019. Contains 328103 sequences. (Running on oeis4.)