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A093615
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E.g.f. equals the ratio of two power series, each with triangular exponents of x.
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1
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0, 1, -1, 3, -15, 85, -570, 4509, -40804, 414864, -4686570, 58245650, -789691134, 11598605460, -183459343613, 3109122970590, -56203651969935, 1079493501290439, -21953265755518782, 471258656426134701, -10648683969964745520, 252651472831081785300
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OFFSET
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0,4
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COMMENTS
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E.g.f. is asymptotic to 1-1/(2x). Compare to e.g.f. of A093523.
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LINKS
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FORMULA
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E.g.f: T1(x)/T0(x), where T0(x) = sum_{n>=0} x^(n*(n+1)/2)/(n*(n+1)/2)! and T1(x) = sum_{n>=0} x^(n*(n+1)/2+1)/(n*(n+1)/2+1)!; T0(r)=0 at r=-0.8851021553904208809237177147294641529670...
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MAPLE
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N:= 10: # to get a(0)..a((N+1)*(N+2)/2-1)
T0:= add(x^(n*(n+1)/2)/(n*(n+1)/2)!, n=0..N):
T1:= add(x^(1+n*(n+1)/2)/(1+n*(n+1)/2)!, n=0..N):
S:= series(T1/T0, x, (N+1)*(N+2)/2):
seq(coeff(S, x, n)*n!, n=0..(N+1)*(N+2)/2-1); # Robert Israel, Jan 01 2018
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PROG
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(PARI) T0(x)=sum(k=0, sqrtint(2*n)+1, x^(k*(k+1)/2)/(k*(k+1)/2)!)
(PARI) T1(x)=sum(k=0, sqrtint(2*n)+1, x^(k*(k+1)/2+1)/(k*(k+1)/2+1)!)
(PARI) a(n)=n!*polcoeff(T1(x)/T0(x)+x*O(x^n), n)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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