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A216034
a(n) = 3^(-1+floor((n+1)/3))*A(n), where A(n) = 3*A(n-1) + A(n-2) - A(n-3)/3 with A(0)=A(1)=3, A(2)=11.
6
1, 1, 11, 35, 115, 1129, 3697, 12105, 118907, 389339, 1274819, 12522481, 41002561, 134255345, 1318783307, 4318113395, 14138868147, 138885370201, 454754601649, 1489010307001, 14626471197755, 47891689912619, 156812530628611, 1540361374197601
OFFSET
0,3
COMMENTS
The Berndt-type sequence number 11a for the argument 2Pi/9 - see A215945 for more details.
FORMULA
G.f.: (1+x+11*x^2-70*x^3+10*x^4-26*x^5-11*x^6-3*x^7-x^8)/(1-105*x^3-33*x^6+x^9). [Bruno Berselli, Oct 02 2012]
PROG
(Magma) i:=24; I:=[3, 3, 11]; A:=[m le 3 select I[m] else 3*Self(m-1)+Self(m-2)-Self(m-3)/3: m in [1..i]]; [3^(-1+Floor(n/3))*A[n]: n in [1..i]]; // Bruno Berselli, Oct 02 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roman Witula, Aug 30 2012
STATUS
approved