|
|
A065896
|
|
Number of composites <= 2*n.
|
|
1
|
|
|
0, 1, 2, 3, 5, 6, 7, 9, 10, 11, 13, 14, 16, 18, 19, 20, 22, 24, 25, 27, 28, 29, 31, 32, 34, 36, 37, 39, 41, 42, 43, 45, 47, 48, 50, 51, 52, 54, 56, 57, 59, 60, 62, 64, 65, 67, 69, 71, 72, 74, 75, 76, 78, 79, 80, 82, 83, 85, 87, 89, 91, 93, 95, 96, 98, 99, 101, 103, 104, 105
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
a(9) = 10, since 18 is the 10th composite number: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18.
|
|
MATHEMATICA
|
Table[2*n-(PrimePi[2*n])-1, {n, 1, 128}]
|
|
PROG
|
(PARI) { for (n=1, 1000, f=2*n; a=f - primepi(f) - 1; write("b065896.txt", n, " ", a) ) } \\ Harry J. Smith, Nov 04 2009
(Haskell)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|