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A081871
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a(1)=1, a(n)=2*a(n-1)+1 if that number is composite, a(n)=a(n-1)+1 otherwise.
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0
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1, 2, 3, 4, 9, 10, 21, 22, 45, 91, 183, 184, 369, 370, 741, 742, 1485, 1486, 2973, 5947, 11895, 23791, 47583, 95167, 190335, 380671, 761343, 1522687, 3045375, 3045376, 6090753, 12181507, 24363015, 48726031, 97452063, 194904127, 389808255, 779616511, 1559233023, 3118466047, 6236932095
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n)=r(n)*2^b(n) where b(n) is an integer sequence and r(n) converges to 1.452148914690155834251....
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MATHEMATICA
| nxt[n_]:=Module[{tst=2n+1}, If[!PrimeQ[tst], tst, n+1]]; NestList[nxt, 1, 40] [From Harvey P. Dale, Dec. 29, 2010]
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CROSSREFS
| Sequence in context: A127150 A098548 A076963 * A180743 A162662 A068334
Adjacent sequences: A081868 A081869 A081870 * A081872 A081873 A081874
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 12 2003
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EXTENSIONS
| Corrected and extended by Harvey P. Dale, Dec. 29, 2010
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