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FORMULA
| a(n)=8^n/2+0^n/2; a(n)=A001045(3n+1)-A001045(3n-1)+0^n/2.
a(n)=A013731(n-1), n>0. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 08 2008]
a(n) = 4 * 8^(n-1), a(0)=1. [From Vincenzo Librandi, Jun 16 2011]
a(n) = Sum_{k, 0<=k<=n} A134309(n,k)*4^k = Sum_{k, 0<=k<=n} A055372(n,k)*3^k. - DELEHAM Philippe, Feb 04 2012
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EXAMPLE
| From Adi Dani, May 28 2011: (Start)
a(2)=32: there are 32 compositions of even natural numbers into 2 parts <=7:
(0,0);
(0,2),(2,0),(1,1);
(0,4),(4,0),(1,3),(3,1),(2,2);
(0,6),(6,0),(1,5),(5,1),(2,4),(4,2),(3,3);
(1,7),(7,1),(2,6),(6,2),(3,5),(5,3),(4,4);
(3,7),(7,3),(4,6),(6,4),(5,5);
(5,7),(7,5),(6,6);
(7,7). (End)
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