|
|
A218151
|
|
a(n) = 2*3^n*5^(n(n-1)/2).
|
|
1
|
|
|
2, 6, 90, 6750, 2531250, 4746093750, 44494628906250, 2085685729980468750, 488832592964172363281250, 572850694879889488220214843750, 3356547040311852470040321350097656250, 98336339071636302833212539553642272949218750
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,1
|
|
COMMENTS
|
a(n) = a(0)*product(i = 1..k) r(i)^C(n,i), with C(n,i) = 0 for all i > n. This is a special case of the geometric-geometric sequence having finite ratios, that is, k consecutive rows of ratios, whose first terms are r(1), r(2), r(3), ..., r(k), the last row (k-th row) being of a constant ratio, with k = 2, a(0) = 2, r(1) = 3, r(2) = 5.
|
|
LINKS
|
|
|
FORMULA
|
a(n) = a(n-1)*3*5^(n-1), a(0) = 2.
|
|
EXAMPLE
|
a(3) = 6750 because a(3)= 2*3^3*5^(3*2/2) = 2*3^3*5^3 = 2*27*125 = 6750.
|
|
MATHEMATICA
|
RecurrenceTable[{a[0]==2, a[n]==a[n-1]3*5^(n-1)}, a, {n, 20}] (* Harvey P. Dale, Jul 30 2019 *)
|
|
PROG
|
(Maxima) A218151(n):=2*3^n*5^(n*(n-1)/2)$
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|