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A055463
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a(n) = 2*a(n-1)*a(n-2) - 3*a(n-3), with a(0) = 0, a(1) = 1, a(2) = 2.
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1
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0, 1, 2, 4, 13, 98, 2536, 497017, 2520869930, 2505830419990012, 12633745110864184300787269, 63316045634407119326463714272245870904666, 1599837563945889048330164752080268110156603845860584259478831024272
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OFFSET
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0,3
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LINKS
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FORMULA
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a(3*n+1) == 1 (mod 12), a(3*n+2) == 2 (mod 12), a(3*n+3) == 4 (mod 12). - Robert Israel, Jan 18 2018
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MAPLE
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A[0]:= 0: A[1]:= 1: A[2]:= 2:
for n from 3 to 17 do A[n]:= 2*A[n-1]*A[n-2]-3*A[n-3] od:
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MATHEMATICA
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a[n_]:= a[n]= If[n<3, n, 2*a[n-1]*a[n-2] -3*a[n-3]];
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PROG
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(Magma)
if n le 2 then return n;
else return 2*a(n-1)*a(n-2) - 3*a(n-3);
end if;
end function;
(SageMath)
if (n<3): return n
else: return 2*a(n-1)*a(n-2) - 3*a(n-3)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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