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%I #9 Jan 25 2017 01:37:08
%S 4,6,9,14,21,26,33,35,38,49,51,58,65,82,85,87,94,111,118,121,123,134,
%T 141,143,145,158,161,166,169,206,209,214,217,219,221,226,237,254,259,
%U 262,265,267,274,287,289,291,298,301,303,305,334,339,341,346,365,382
%N a(1) = 4; a(n) = smallest semiprime such that a(n) - a(n-1) is prime.
%C First differences: 2, 3, 5, 7, 5, 7, 2, 3, 11, 2, 7, 7, 17, 3, 2, 7, 17, 7, 3, 2, 11, 7, 2, 2, 13, 3, 5, 3, 37, 3, 5, 3, 2, 2, 5, 11, 17, 5, 3, 3, 2, 7, 13, 2, 2, 7, 3, 2, 2 (all primes).
%H Zak Seidov, <a href="/A175587/b175587.txt">Table of n, a(n) for n = 1..1000</a>
%t NestList[(p = 2; While[2 != PrimeOmega[q = # + p], p = NextPrime[p]]; q) &, 4, 50]
%o (PARI) nxt(n)=forprime(p=2,, if(bigomega(n+p)==2, return(n+p))) \\ _Charles R Greathouse IV_, Jan 25 2017
%Y Cf. A001358 (semiprimes).
%K nonn
%O 1,1
%A _Zak Seidov_, Jul 17 2010