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%I #5 Apr 29 2018 18:13:38
%S 1,5,11,20,30,44,59,80,102,127,153,186,220,255,293,332,378,427,478,
%T 533,590,648,710,775,844,918,995,1077,1162,1248,1335,1426,1519,1613,
%U 1708,1814,1925,2040,2158,2277,2398,2520,2643,2772,2905,3039,3180,3322,3465
%N 1 + sum of first n semiprimes.
%C First differences are the sequence of semiprimes (A001358). Hence a(n) is the least positive sequence whose first differences are the sequence of semiprimes. Primes in this sequence include: a(1) = 5, a(2) = 11, a(6) = 59, a(9) = 127, a(14) = 293, a(33) = 1613. Semiprimes in this sequence include: a(17) = 427 = 7 * 61, a(18) = 478 = 2 * 239, a(19) = 533 = 13 * 41, a(26) = 995 = 5 * 199, a(27) = 1077 = 3 * 359, a(35) = 1814 = 2 * 907, a(42) = 2643 = 3 * 881, a(45) = 3039 = 3 * 1013.
%F a(0) = 1; for n>0, a(n) = 1 + A062198(n).
%t Accumulate[Join[{1},Select[Range[200],PrimeOmega[#]==2&]]] (* _Harvey P. Dale_, Apr 29 2018 *)
%Y Cf. A001358, A062198, A110209, A110226.
%K easy,nonn
%O 0,2
%A _Jonathan Vos Post_, Sep 06 2005
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