|
Search: id:A080860
|
|
|
| A080860 |
|
Generalized polygonal numbers. |
|
+0
2
|
|
| 1, 16, 51, 106, 181, 276, 391, 526, 681, 856, 1051, 1266, 1501, 1756, 2031, 2326, 2641, 2976, 3331, 3706, 4101, 4516, 4951, 5406, 5881, 6376, 6891, 7426, 7981, 8556, 9151, 9766, 10401, 11056, 11731, 12426, 13141, 13876, 14631, 15406, 16201, 17016, 17851
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
COMMENT
|
Column T(n,5) of A080853.
|
|
FORMULA
|
a(n) = C(5, 0)+C(5, 1)n+C(5, 2)n^2 = 10n^2+5n+1 G.f. (C(4, 0)+(C(6, 2)-2)*x+C(4, 2)*x^2)/(1-x)^3 = (1+13x+6x^2)/(1-x)^3
a(n)=20*n+a(n-1)-25 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 16 2009]
|
|
EXAMPLE
|
For n=2, a(2)=20*2+1-25=16; n=3, a(3)=20*3+16-25=51; n=4, a(4)=20*4+51-25=106 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 16 2009]
|
|
CROSSREFS
|
Sequence in context: A030688 A121863 A121864 this_sequence A044118 A044499 A009953
Adjacent sequences: A080857 A080858 A080859 this_sequence A080861 A080862 A080863
|
|
KEYWORD
|
easy,nonn,new
|
|
AUTHOR
|
Paul Barry (pbarry(AT)wit.ie), Feb 23 2003
|
|
|
Search completed in 0.005 seconds
|
