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A078344
a(1)=1; a(2)=2; a(3)=3; a(n) = Sum_{k=3..n-1} (a(k) + a(k-1) + a(k-2)).
0
1, 2, 3, 6, 17, 43, 109, 278, 708, 1803, 4592, 11695, 29785, 75857, 193194, 492030, 1253111, 3191446, 8128033, 20700623, 52720725, 134270106, 341961560, 870913951, 2218059568, 5648994647, 14386962813, 36640979841, 93317917142
OFFSET
1,2
FORMULA
a(n) is asymptotic to a*b^n where a = 0.1570450524507584150437292... and b is the real root of: x^3 - 2*x^2 - x - 1; b = 2.546818276884082079135997..
a(n) = 2*a(n-1)+a(n-2)+a(n-3) for n>4. G.f.: x*(3*x^3+2*x^2-1) / (x^3+x^2+2*x-1). - Colin Barker, Jun 24 2013
CROSSREFS
Sequence in context: A204514 A338594 A375565 * A024498 A319283 A325298
KEYWORD
nonn,easy
AUTHOR
Benoit Cloitre, Nov 22 2002
STATUS
approved

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