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 A110208 1 + sum of first n semiprimes. 2
 1, 5, 11, 20, 30, 44, 59, 80, 102, 127, 153, 186, 220, 255, 293, 332, 378, 427, 478, 533, 590, 648, 710, 775, 844, 918, 995, 1077, 1162, 1248, 1335, 1426, 1519, 1613, 1708, 1814, 1925, 2040, 2158, 2277, 2398, 2520, 2643, 2772, 2905, 3039, 3180, 3322, 3465 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS 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. LINKS FORMULA a(0) = 1; for n>0, a(n) = 1 + A062198(n). MATHEMATICA Accumulate[Join[{1}, Select[Range, PrimeOmega[#]==2&]]] (* Harvey P. Dale, Apr 29 2018 *) CROSSREFS Cf. A001358, A062198, A110209, A110226. Sequence in context: A304502 A190743 A331133 * A034308 A032527 A212978 Adjacent sequences:  A110205 A110206 A110207 * A110209 A110210 A110211 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Sep 06 2005 STATUS approved

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Last modified September 16 05:49 EDT 2021. Contains 347469 sequences. (Running on oeis4.)