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A048437
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Take the first n numbers written in base 5, concatenate them, then convert from base 5 to base 10.
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18
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1, 7, 38, 194, 4855, 121381, 3034532, 75863308, 1896582709, 47414567735, 1185364193386, 29634104834662, 740852620866563, 18521315521664089, 463032888041602240, 11575822201040056016, 289395555026001400417
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OFFSET
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1,2
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COMMENTS
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The first three primes in this sequence occur for n = 2 (a(2) = 7), n = 113 (a(113) = 7.4484...*10^216), n = 162 (a(162) = 1.5188...*10^346). - Kurt Foster, Oct 24 2015 [Comment added by N. J. A. Sloane, Oct 25 2015]
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LINKS
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EXAMPLE
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a(7) = 1 2 3 4 10 11 12 = 3034532_10.
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MATHEMATICA
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If[STARTPOINT==1, n={}, n=Flatten[IntegerDigits[Range[STARTPOINT-1], 5]]]; Table[AppendTo[n, IntegerDigits[w, 5]]; n=Flatten[n]; FromDigits[n, 5], {w, STARTPOINT, ENDPOINT}] (* Dylan Hamilton, Aug 11 2010 *)
f[n_]:= FromDigits[Flatten@IntegerDigits[Range@n, 5], 5]; Array[f, 20] (* Vincenzo Librandi, Dec 30 2012 *)
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PROG
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(Magma) [n eq 1 select 1 else Self(n-1)*5^(1+Ilog(5, n))+n: n in [1..20]]; // Vincenzo Librandi, Dec 30 2012
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CROSSREFS
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Concatenation of first n numbers in other bases: 2: A047778, 3: A048435, 4: A048436, 5: this sequence, 6: A048438, 7: A048439, 8: A048440, 9: A048441, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447.
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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