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A039941
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Alternately add and multiply.
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10
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0, 1, 1, 1, 2, 2, 4, 8, 12, 96, 108, 10368, 10476, 108615168, 108625644, 11798392572168192, 11798392680793836, 139202068568601556987554268864512, 139202068568601568785946949658348, 19377215893777651167043206536157390321290709180447278572301746176
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OFFSET
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0,5
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LINKS
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FORMULA
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a(2n) = a(2n-1) + a(2n-2); a(2n+1) = a(2n-1)*a(2n); a(0) = 0; a(1) = 1
a(n) = {a(n-1) + a(n-2), n even, a(n-1)*a(n-2), n odd}; a(0)=0; a(1)=1.
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MATHEMATICA
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nxt[{n_, a_, b_}]:={n+1, b, If[EvenQ[n], a+b, a*b]}; Join[{0}, Transpose[ NestList[ nxt, {0, 0, 1}, 20]][[3]]] (* Harvey P. Dale, Aug 23 2013 *)
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PROG
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(PARI) a(n)=if(n<2, n>0, if(n%2, a(n-1)*a(n-2), a(n-1)+a(n-2)))
(Haskell)
a039941 n = a039941_list !! (n-1)
a039941_list = 0 : 1 : zipWith3 ($)
(cycle [(+), (*)]) a039941_list (tail a039941_list)
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CROSSREFS
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KEYWORD
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easy,nonn,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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