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A096057
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a(1) = 1, a(n) = least prime divisor of b(n), where b(1) = 1, b(n) = n*b(n-1) + 1 = A002627(n).
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1
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1, 3, 2, 41, 2, 1237, 2, 29, 2, 43, 2, 5, 2, 5, 2, 35951249665217, 2, 28001, 2, 1409, 2, 5, 2, 5, 2, 47, 2, 661, 2, 13, 2, 5, 2, 5, 2, 13, 2, 13, 2, 73, 2, 5, 2, 5, 2, 71, 2, 2437159, 2, 31, 2, 5, 2, 5, 2, 13, 2, 3020497643, 2, 23, 2, 5, 2, 5, 2, 5672529813439, 2, 15336863
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(4) = 41 because b(3) = 3*b(2)+1 = 3*3+1 = 10 and 4*10+1 = 41, which is prime.
b(n) = 1, 3, 10, 41, ... with least prime divisors a(n) = 1, 3, 2, 41, ....
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MATHEMATICA
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nxt[{n_, a_}]:={n+1, a(n+1)+1}; FactorInteger[#][[1, 1]]&/@NestList[nxt, {1, 1}, 40][[All, 2]] (* The program generates the first 41 terms of the sequence. *) (* Harvey P. Dale, Jun 21 2022 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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