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 A073839 Sum of the composite numbers between n and 2n (both inclusive). 2
 0, 4, 10, 18, 33, 45, 53, 84, 94, 105, 138, 162, 201, 256, 272, 289, 340, 411, 431, 510, 532, 555, 624, 672, 747, 825, 853, 937, 1024, 1084, 1116, 1243, 1342, 1377, 1482, 1519, 1557, 1708, 1825, 1866, 1989, 2073, 2202, 2377, 2423, 2561, 2702, 2893, 2943 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is the sum of A075084(n) composite numbers (A002808). - Michel Marcus, Aug 26 2015 LINKS Table of n, a(n) for n=1..49. EXAMPLE a(6) = 6+8+9+10+12 = 45. MAPLE for n from 1 to 150 do l := 0:for j from n to 2*n do if not isprime(j) then l := l+j:fi:od:a[n] := l:od:a[1] := 0:seq(a[j], j=1..150); MATHEMATICA cs[x_] := Flatten[Position[Table[PrimeQ[j], {j, x, 2*x}], False]]+x-1; sucs[x_] := Apply[Plus, cs[x]]; Table[sucs[w], {w, 1, 128}] Join[{0}, Table[Plus @@ Select[Range[n, 2 n], ! PrimeQ[#] &], {n, 2, 49}]] (* Jayanta Basu, Aug 12 2013 *) PROG (PARI) a(n) = my(s=0); forcomposite (c=n, 2*n, s+=c); s; \\ Michel Marcus, Aug 26 2015 CROSSREFS Cf. A002808, A073840, A075084. Sequence in context: A008011 A009867 A019455 * A225610 A009921 A050188 Adjacent sequences: A073836 A073837 A073838 * A073840 A073841 A073842 KEYWORD nonn AUTHOR Amarnath Murthy, Aug 13 2002 EXTENSIONS More terms from Sascha Kurz and Labos Elemer, Aug 14 2002 STATUS approved

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Last modified December 4 21:08 EST 2023. Contains 367565 sequences. (Running on oeis4.)