|
| |
| |
|
|
|
1, 3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51, 55, 59, 63, 67, 71, 75, 79, 83, 87, 91, 95, 99, 103, 107, 111, 115, 119, 123, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179, 183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| Draw 1 circle: we see 1 region. Draw 2 identical circles, the second with center on the other, we see 3 regions. Draw 3 identical circles, the third with centre on both the others, we see 7 regions, ...
|
|
|
LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
|
|
|
FORMULA
| a(n+1) = 4n - 1 = sum of n-th odd natural number and n-th even natural number = A005408(n-1) + A005843(n) for n >= 1. [From Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Aug 15 2009]
G.f.: x*(x+2*x^2+1)/(x-1)^2. [R. J. Mathar, Dec 08 2010]
|
|
|
CROSSREFS
| Sequence in context: A172338 A189787 A004767 * A118894 A194397 A039957
Adjacent sequences: A131095 A131096 A131097 * A131099 A131100 A131101
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Hans Isdahl (hansi(AT)nordtroms.net), Sep 24 2007
|
|
|
EXTENSIONS
| Edited by N. J. A. Sloane, Jun 29 2009
|
| |
|
|
