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A003073
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A nonlinear recurrence.
(Formerly M0282)
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1
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1, 1, 2, 2, 3, 4, 5, 7, 9, 11, 14, 18, 23, 29, 38, 47, 59, 76, 95, 120, 154, 191, 241, 310, 383, 483, 620, 767, 968, 1242, 1535, 1937, 2486, 3071, 3875, 4972, 6143, 7752, 9946, 12287, 15505, 19894, 24575, 31011, 39788, 49151, 62024, 79578, 98303
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OFFSET
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0,3
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REFERENCES
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D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 3, p. 208.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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MATHEMATICA
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A003073[n_]:= If[Mod[n, 3]==0, Floor[3*2^Floor[n/3]/2] - Boole[Floor[n/3] >0], If[Mod[n, 3]==2, 2*Floor[17*2^Floor[n/3]/14] +Boole[Floor[n/3] == 2], Floor[53*2^Floor[n/3]/28] - Boole[Floor[n/3] >2] ]];
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PROG
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(PARI) a(n)=local(k); k=n\3; if(n%3==0, 3*2^k\2-(k>0), if(n%3==2, 2*(17*2^k\14)+(k==2), 53*2^k\28-(k>2))) /* Michael Somos, May 04 2000 */
(SageMath)
if (n%3==0): return ((3*2^(n//3))//2) - int((n//3)>0)
elif (n%3==2): return 2*((17*2^(n//3))//14) + int((n//3)==2)
else: return ((53*2^(n//3))//28) - int((n//3)>2)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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