A075878 Sum of coefficients of (x1)^(2i(1))*(x2)^(2i(2))*(x3)^(2i(3))*(x4)^(2i(4)) for {(i1),(i2),(i3),(i4)}=0,1,2,... : sum(i)=2n in the expansion of (x1+x2+x3+x4)^(2n) where n=1,2,3,...

4, 40, 544, 8320, 131584, 2099200, 33562624, 536903680, 8590065664, 137439477760, 2199025352704, 35184380477440

Offset

0,1

Comments

For k=3, the sequence divided by 3 is equal to A066443.

Links

Table of n, a(n) for n=0..11.

Formula

a(n, 4) = 2^(1-4)*(sum(r=0 to Floor((4-1)/2))Binomial(4, r)*(4-2*r)^2n a(n, k) = 2^(1-k)*(sum(r=0 to Floor((k-1)/2))Binomial(k, r)*(k-2*r)^2n for k=1, 2, 3, 4, ...

Crossrefs

Cf. A066443.

Essentially same as A092812. - Kang Seonghoon (lifthrasiir(AT)gmail.com), Oct 09 2008

Sequence in context: A074637 A371676 A379244 * A092812 A349516 A290575

Adjacent sequences: A075875 A075876 A075877 * A075879 A075880 A075881

Keyword

easy,nonn

Author

Jan Hagberg (jan.hagberg(AT)stat.su.se), Oct 16 2002

Extensions

Corrected by T. D. Noe, Nov 07 2006

Status

approved