|
| |
|
|
A125527
|
|
Number of semiprimes <= 2^n.
|
|
6
| |
|
|
0, 1, 2, 6, 10, 22, 42, 82, 157, 304, 589, 1124, 2186, 4192, 8110, 15658, 30253, 58546, 113307, 219759, 426180, 827702, 1608668, 3129211, 6091437, 11868599, 23140878, 45150717, 88157689, 172235073, 336717854, 658662065, 1289149627, 2524532330
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,3
|
|
|
LINKS
| Robert G. Wilson v, Table of n, a(n) for n = 1..49 [File corrected Mar 12 2007]
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
|
|
|
FORMULA
| a(n) = A072000(2^n). - R. J. Mathar, Aug 26 2011
|
|
|
MATHEMATICA
| SemiPrimePi[n_] := Sum[ PrimePi[ n/Prime@i] - i + 1, {i, PrimePi@ Sqrt@n}]; Table[ SemiPrimePi[2^n], {n, 47}]
|
|
|
CROSSREFS
| Cf. A126279, A066265, A007053, A127396.
Sequence in context: A055745 A167512 A055895 * A200572 A049750 A134016
Adjacent sequences: A125524 A125525 A125526 * A125528 A125529 A125530
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 29 2006
|
| |
|
|
