|
Search: id:A140481
|
|
|
| A140481 |
|
a(1) = 1; for n >= 1, a(n+1) is obtained by adding to a(n) the a(n)-th smallest number not dividing a(n). |
|
+0
2
|
|
| 1, 3, 8, 20, 46, 96, 204, 420, 864, 1752, 3520, 7068, 14160, 28360, 56736, 113508, 227040, 454176, 908424, 1816944, 3633908, 7267828, 14535662, 29071328, 58142704, 116285418, 232570884, 465141864, 930283760, 1860567600
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
FORMULA
|
a(n+1) = 2*a(n) + tau(a(n)) (cf. A000005). - Hans Havermann and Franklin T. Adams-Watters, Jun 25 2008. Using a(n+1) = a(n) + tau(a(n)) would give A064491.
|
|
EXAMPLE
|
The smallest number not dividing 1 is 2, so a(2) = 1+2 = 3.
The numbers not dividing 3 are 2, 4, 5, 6, ..., so a(3) = 3+5 = 8.
The numbers not dividing 8 are 3, 5, 6, 7, 9, 10, 11, 12, ..., so a(4) = 8+12 = 20.
|
|
CROSSREFS
|
Cf. A000005, A064491, A140482.
Sequence in context: A134393 A014628 A034504 this_sequence A027928 A026624 A026690
Adjacent sequences: A140478 A140479 A140480 this_sequence A140482 A140483 A140484
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Eric Angelini (Eric.Angelini(AT)kntv.be), Jun 25 2008
|
|
EXTENSIONS
|
More terms from Hans Havermann (pxp(AT)rogers.com), Jun 25 2008
|
|
|
Search completed in 0.002 seconds
|
