|
|
A217628
|
|
a(n) = 3^((n-1)*(n+2)/2).
|
|
2
|
|
|
1, 9, 243, 19683, 4782969, 3486784401, 7625597484987, 50031545098999707, 984770902183611232881, 58149737003040059690390169, 10301051460877537453973547267843, 5474401089420219382077155933569751763, 8727963568087712425891397479476727340041449
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(1) = 1, a(n) = a(n-1) * 3^n.
G.f.: G(0)/(2*x^3) - 1/(3*x)- 1/(3*x^2)- 1/(2*x^3), where G(k)= 1 + 3^(k-1)*x/(1 - 1/(1 + 1/G(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Jul 28 2013
|
|
MATHEMATICA
|
Table[3^((n-1) * (n+2)/2), {n, 1, 30}]
|
|
PROG
|
(Magma) I:=[1]; [n le 1 select I[n] else Self(n-1)*3^n: n in [1..20]]
(Maxima) A217628[n]:=3^((n-1)*(n+2)/2)$
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|