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A283676
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a(0)=0, then a(n) = smallest odd k > a(n-1) such that 6*k^prime(n)-1 is prime.
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1
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0, 1, 9, 15, 47, 89, 357, 537, 697, 1037, 1257, 1643, 1723, 1995, 2333, 2357, 2863, 3395, 3593, 4795, 5187, 5349, 5469, 5759, 5859, 6339, 6573, 8097, 8653, 8683, 8773, 8827, 8947, 10213, 10609, 10959, 11407, 12325, 13365, 14109, 15549, 18589, 18639, 19343
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OFFSET
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0,3
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LINKS
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EXAMPLE
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6*1^prime(1)-1 = 5 prime so a(1)=1, prime (2)=3, 6*3^3-1 = 161 composite, 6*5^3-1 = 749 composite, 6*7^3-1 = 2057 composite, 6*9^3-1 = 4373 prime so a(2) = 9.
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MATHEMATICA
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a[0] = 0; a[n_] := a[n] = Module[{k = Boole[OddQ@ #] + # + 1 &@ a[n - 1]}, While[! PrimeQ[6*k^Prime[n] - 1], k += 2]; k]; Table[a@ n, {n, 0, 43}] (* Michael De Vlieger, Mar 15 2017 *)
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PROG
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(PARI) foddk(n, k) = {while (! isprime(6*k^prime(n)-1), k+=2); k; }
lista(nn) = {k = 1; for (n=1, nn, k = foddk(n, k); print1(k, ", "); k += 2; ); } \\ Michel Marcus, Mar 18 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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