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A087555
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a(n) = largest prime that is the concatenation of two numbers whose sum is n.
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1
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11, 0, 31, 41, 0, 61, 71, 0, 73, 101, 0, 211, 311, 0, 313, 107, 0, 811, 911, 0, 211, 1013, 0, 1213, 1511, 0, 1117, 1811, 0, 2011, 2111, 0, 2311, 2411, 0, 2017, 2711, 0, 2713, 3011, 0, 2617, 431, 0, 3511, 3413, 0, 3613, 3911, 0, 4111, 4211, 0, 541, 3917, 0, 4513, 4217
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OFFSET
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2,1
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COMMENTS
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a(3k) = 0. Conjecture: No other term is zero.
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LINKS
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EXAMPLE
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a(10) = 73, the Partitions of 10 are (1,9), (2,8), 3,7), (4,6), (5,5) and the primes obtained are 19,37 and 73.
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MATHEMATICA
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lpc[n_]:=Max[Select[FromDigits[Flatten[IntegerDigits[#]]]&/@(Flatten[{#, Reverse[#]}&/@ IntegerPartitions[ n, {2}], 1]), PrimeQ]]; Array[lpc, 60, 2]/.(-\[Infinity])->0 (* Harvey P. Dale, Aug 02 2024 *)
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CROSSREFS
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KEYWORD
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base,nonn,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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