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A056589
Third column sequence of unsigned triangle A056588.
4
1, 4, 16, 53, 166, 492, 1413, 3960, 10912, 29689, 80026, 214196, 570289, 1512300, 3998160, 10545741, 27766942, 73012060, 191785165, 503378480, 1320425536, 3462057009, 9074076786, 23776857828, 62289901081, 163159711492
OFFSET
0,2
FORMULA
a(n)= -A056588(n+2, 2), n >= 0. a(n)= -2^(n+3)+F(n+4)*(F(n+3)+1), F(n)=A000045(n).
G.f.(1-x+x^2)/((1-2*x)*(1+x)*(1-3*x+x^2)*(1-x-x^2))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang Jul 10 2000
STATUS
approved