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A049390
Expansion of (1-25*x)^(4/5).
0
1, -20, -50, -500, -6875, -110000, -1925000, -35750000, -692656250, -13853125000, -283989062500, -5937953125000, -126181503906250, -2717755468750000, -59208244140625000, -1302581371093750000
OFFSET
0,2
FORMULA
G.f.: (1-25*x)^(4/5).
a(n) = 5^n/n! * product[ k=0..n-1 ] (5*k-4).
a(n) ~ -4/5*Gamma(1/5)^-1*n^(-9/5)*5^(2*n)*{1 + 18/25*n^-1 + ...}. - Joe Keane (jgk(AT)jgk.org), Nov 24 2001
EXAMPLE
(1-x)^(4/5) = 1 - 4/5*x - 2/25*x^2 - 4/125*x^3 - ...
MATHEMATICA
CoefficientList[Series[(1-25x)^(4/5), {x, 0, 20}], x] (* Harvey P. Dale, Dec 14 2017 *)
CROSSREFS
Cf. A034688.
Sequence in context: A241609 A331753 A345124 * A220040 A128905 A276135
KEYWORD
sign,easy
AUTHOR
Joe Keane (jgk(AT)jgk.org)
EXTENSIONS
Definition adjusted by Harvey P. Dale, Dec 14 2017.
STATUS
approved