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1, 7, 38, 187, 874, 3958, 17548, 76627, 330818, 1415650, 6015316, 25413342, 106853668, 447472972, 1867450648, 7770342787, 32248174258, 133530264682, 551793690628, 2276098026922, 9373521044908, 38546133661492, 158301250009768, 649328801880622
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = 2^(1 + 2*n)*((2*Gamma(5/2 + n))/(sqrt(Pi)*Gamma(2 + n)) - 1).
a(n) ~ 4^(n+1)*(sqrt(n/Pi) - 1/2).
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MAPLE
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a := n -> 2^(1 + 2*n)*((2*GAMMA(5/2 + n))/(sqrt(Pi)*GAMMA(2 + n)) - 1):
seq(a(n), n=0..23);
# alternative
2^(2*n)*(doublefactorial(2*n+3)/(1+n)/doublefactorial(2*n)-2) ;
end proc:
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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