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Search: id:A084476
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| A084476 |
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Least k such that 10^(2n-1)+k is a brilliant number. |
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+0
3
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| 0, 3, 13, 43, 81, 147, 73, 3, 831, 49, 987, 691, 183, 4153, 279, 667, 709, 277, 1687, 997, 1207, 91, 1411, 393, 951, 9793, 2217, 6229, 2317, 213, 399, 19, 2317, 609, 2607, 11901, 10563, 5473, 3, 5923, 17527, 8569, 16701, 11989, 9757, 6489, 3489, 2899
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Least brilliant number greater than 10^(2n) is {10^n+A033873(n)}^2. The web site also lists the two prime factors.
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LINKS
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Dario Alejandro Alpern, Brilliant numbers
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EXAMPLE
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a(3)=13 because 10^5+13 = 100013 = 103*971.
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MATHEMATICA
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NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; LengthBase10[n_] := Floor[ Log[10, n] + 1]; f[n_] := Block[{k = 0}, If[ EvenQ[n] && n > 1, NextPrim[ 10^(n/2)]^2 - 10^(n/2), While[fi = FactorInteger[10^n + k]; Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ fi] != 2 || Length[ Union[ LengthBase10 /@ Flatten[ Table[ # [[1]], {1}] & /@ fi]]] != 1, k++ ]; k]]; Table[ f[2n + 1], {n, 1, 24}]
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CROSSREFS
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Cf. A078972., A084475.
Sequence in context: A041499 A093923 A138249 this_sequence A049173 A049156 A054771
Adjacent sequences: A084473 A084474 A084475 this_sequence A084477 A084478 A084479
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KEYWORD
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base,hard,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 27 2003
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