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A034969
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a(1) = a(2) = 1, a(n) is largest prime factor of concatenation of a(n - 2) and a(n - 1).
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2
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1, 1, 11, 37, 379, 37379, 130369, 463, 12277, 4210207, 1015309, 42102071015309, 7522851571, 39903394005601130021, 747580650949733, 2601211879473948668292638737, 16287160151410310678021523908384898241043, 37391601140774556436246253
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OFFSET
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1,3
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LINKS
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EXAMPLE
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a(6) = 37379 because the concatenation of a(4) and a(5) is 37379, a prime number.
a(7) = 130369 because the concatenation of a(5) and a(6) is 37937379 = 3 * 97 * 130369.
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MATHEMATICA
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nxt[{a_, b_}]:={b, FactorInteger[FromDigits[Flatten[IntegerDigits[ {a, b}]]]][[-1, 1]]}; Transpose[NestList[nxt, {1, 1}, 18]][[1]] (* Harvey P. Dale, Nov 24 2012 *)
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CROSSREFS
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KEYWORD
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nonn,base,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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