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A072342
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a(n) = the least natural number k such that k*reverse(n) + 1 is prime.
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0
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1, 1, 2, 1, 2, 1, 4, 2, 2, 1, 2, 2, 10, 2, 2, 6, 8, 2, 6, 1, 1, 1, 3, 1, 1, 5, 1, 1, 3, 2, 4, 2, 2, 4, 2, 2, 4, 2, 4, 1, 2, 3, 3, 2, 2, 3, 2, 4, 3, 2, 2, 4, 2, 4, 6, 2, 2, 12, 2, 1, 1, 2, 1, 1, 2, 1, 3, 2, 1, 4, 6, 4, 4, 6, 4, 4, 6, 4, 4, 2, 1, 1, 5, 2, 1, 2, 1, 1, 2, 2, 10, 2, 2, 4, 12, 2, 4, 2, 2, 1, 6, 8
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Conjecture: a(n) is less than or equal to n for all n.
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EXAMPLE
| Reverse(12) = 21 and the least natural number k such that 21 k + 1 is prime is k = 2; so a(12) = 2.
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MATHEMATICA
| f[n_] := Module[{i}, i = 0; While[ ! PrimeQ[i*FromDigits[Reverse[IntegerDigits[n]]]+ 1], i++ ]; i]; Table[f[i], {i, 1, 150}]
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CROSSREFS
| Sequence in context: A205403 A080825 A034693 * A066389 A077191 A050363
Adjacent sequences: A072339 A072340 A072341 * A072343 A072344 A072345
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KEYWORD
| base,nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jul 16 2002
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