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A086407
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a[1]=1; a[n+1]=a[n]-1 if mod[prime[a[n]],6]=5, else a[n+1]=a[n]+4.
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2
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1, 5, 4, 8, 12, 16, 15, 14, 18, 22, 26, 25, 29, 33, 32, 31, 35, 34, 38, 42, 46, 50, 54, 53, 57, 56, 55, 54, 53, 57, 56, 55, 54, 53, 57, 56, 55, 54, 53, 57, 56, 55, 54, 53, 57, 56, 55, 54, 53, 57, 56, 55, 54
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OFFSET
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1,2
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COMMENTS
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There is a cycle ...54,53,57,56,55,54,...
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LINKS
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EXAMPLE
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a(3)=4 because a(2)=5, prime[5]=11=1 (mod 6) and a(3)=a(2)-1
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MATHEMATICA
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b=1; Prepend[Table[b+=If[Mod[Prime[b], 6]\[Equal]5, -1, 4], {i, 32}], 1]
nxt[a_]:=If[Mod[Prime[a], 6]==5, a-1, a+4]; NestList[nxt, 1, 60] (* Harvey P. Dale, May 29 2013 *)
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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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