A073839 Sum of the composite numbers between n and 2n (both inclusive).

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

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