|
Search: id:A069178
|
|
|
| A069178 |
|
Centered 21-gonal numbers. |
|
+0
2
|
|
| 1, 22, 64, 127, 211, 316, 442, 589, 757, 946, 1156, 1387, 1639, 1912, 2206, 2521, 2857, 3214, 3592, 3991, 4411, 4852, 5314, 5797, 6301, 6826, 7372, 7939, 8527, 9136
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
LINKS
|
E. Weisstein, Centered Polygonal Numbers
Index entries for sequences related to centered polygonal numbers
|
|
FORMULA
|
a(n) = (21n^2 - 21n + 2)/2
a(n)=21*n+a(n-1)-21 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 16 2009]
|
|
EXAMPLE
|
For n=2, a(2)=21*2+1-21=22; n=3, a(3)=21*3+22-21=64; n=4, a(4)=21*4+64-21=127 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 16 2009]
|
|
CROSSREFS
|
Cf. A005448, A001844, A005891, A003215, A069099, A069125, A069133, A069126, A069127, A069128, A069129, A069130, A069131, A069132.
Sequence in context: A156797 A051874 A140390 this_sequence A081929 A124715 A126376
Adjacent sequences: A069175 A069176 A069177 this_sequence A069179 A069180 A069181
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Terrel Trotter, Jr. (ttrotter(AT)telesal.net), Apr 09 2002
|
|
|
Search completed in 0.002 seconds
|
