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A121480
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Take b(0)=n, for i>0 if b(i-1) is odd prime then b(i)=(b(i-1)+1)/2 otherwise b(i)=b(i-1)+1. For all n sequence b(i) ends with 2. The sequence gives a(n) = a number of steps from n to 2, a(n)=i when b(i)=2.
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2, 1, 0, 1, 3, 2, 5, 4, 9, 8, 7, 6, 6, 5, 12, 11, 10, 9, 9, 8, 10, 9, 8, 7, 17, 16, 15, 14, 13, 12, 12, 11, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 10, 9, 21, 20, 19, 18, 20, 19, 18, 17, 16, 15, 18, 17, 16, 15, 14, 13, 13, 12, 18, 17, 16, 15, 14, 13, 14, 13, 12, 11, 11, 10, 17, 16, 15
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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EXAMPLE
| a(8)=9 because b(0)=8, b(1)=9, b(2)=10, 11, 6, 7, 4, 5, 3, b(9)=2;
a(10)=7 because b(0)=10, b(1)=11, 6, 7, 4, 5, 3, b(7)=2, etc
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MATHEMATICA
| b=c=1; re={{0, 2}, {1, 1}, {2, 0}}; Do[i=0; a=n; While[a!=2, i++; If[PrimeQ[a], a=(a+c)/2, a=a+b]]; AppendTo[re, i], {n, 3, 100}]; re
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CROSSREFS
| Sequence in context: A078806 A173438 A103493 * A082601 A077593 A119337
Adjacent sequences: A121477 A121478 A121479 * A121481 A121482 A121483
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Aug 02 2006
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