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A073666
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Rearrangement of natural numbers such that a(k)*a(k+1) + 1 is a prime for all k.
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4
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1, 2, 3, 4, 7, 6, 5, 8, 9, 12, 13, 10, 15, 14, 17, 18, 11, 30, 19, 22, 16, 21, 20, 23, 26, 33, 34, 27, 28, 24, 25, 42, 31, 36, 32, 29, 38, 39, 48, 37, 40, 43, 46, 51, 50, 45, 52, 49, 54, 44, 47, 56, 41, 62, 59, 60, 53, 66, 35, 68, 57, 58, 55, 70, 61, 76, 63, 74, 69, 72, 71, 98
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a[1]=1; a[n_]:=a[n]=(For[c=Sort[Table[a[k], {k, n-1}]]; d=Append[c, Last[c]+1]; m=First[Complement[Range[Last[d]], c]], MemberQ[c, m]||!PrimeQ[m*a[n-1]+1], m++ ];m) (Farideh Firoozbakht (mymontain(AT)yahoo.com), Apr 14 2004)
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MATHEMATICA
| a[1]=1; a[n_]:=a[n]=(For[c=Sort[Table[a[k], {k, n-1}]]; d=Append[c, Last[c]+1]; m=First[Complement[Range[Last[d]], c]], MemberQ[c, m]||!PrimeQ[m*a[n-1]+1], m++ ]; m); Table[a[k], {k, 70}] (Farideh Firoozbakht (mymontain(AT)yahoo.com), Apr 14 2004)
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CROSSREFS
| Cf. A092842, A081942, A081943, A092829.
Cf. A073667.
Sequence in context: A055265 A117922 A201543 * A092842 A072028 A072026
Adjacent sequences: A073663 A073664 A073665 * A073667 A073668 A073669
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 10 2002
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EXTENSIONS
| More terms from Jason Earls (zevi_35711(AT)yahoo.com), Aug 26 2002
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