A015503 - cp's OEIS frontend

A015503 a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).

n	a(n)
1	1
2	1
3	6
4	132
5	11352
6	3882384
7	5303336544
8	28966824203328
9	632809241545903488
10	55296137144764138588416
11	19327437631660830304254690816
12	27021729207700270170039091739231232
13	151116480551518237100547636877027177224192

[1, 1, 6, 132, 11352, 3882384, 5303336544, 28966824203328, 632809241545903488, 55296137144764138588416, 19327437631660830304254690816, 27021729207700270170039091739231232, 151116480551518237100547636877027177224192]

cp's OEIS Frontend

A015503 a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).

Table of values

List of values