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 A048435 Take the first n numbers written in base 3, concatenate them, then convert from base 3 to base 10. 17
 1, 5, 48, 436, 3929, 35367, 318310, 2864798, 77349555, 2088437995, 56387825876, 1522471298664, 41106725063941, 1109881576726421, 29966802571613382, 809103669433561330, 21845799074706155927, 589836575017066210047 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The first three primes in this sequence occur for n = 2 (a(2) = 5), n = 5 (a(5) = 3929), and n = 82 (a(82) = 1.1247...*10^140). - Kurt Foster, Oct 24 2015 [Comment added by N. J. A. Sloane, Oct 25 2015] LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..200 EXAMPLE a(6): (1)(2)(10)(11)(12)(20) = 1210111220_3 = 35367. MATHEMATICA If[STARTPOINT==1, n={}, n=Flatten[IntegerDigits[Range[STARTPOINT-1], 3]]]; Table[AppendTo[n, IntegerDigits[w, 3]]; n=Flatten[n]; FromDigits[n, 3], {w, STARTPOINT, ENDPOINT}] (* Dylan Hamilton, Aug 09-04 2010 *) f[n_]:= FromDigits[Flatten@IntegerDigits[Range@n, 3], 3]; Array[f, 20] (* Vincenzo Librandi, Dec 30 2012 *) PROG (MAGMA) [n eq 1 select 1 else Self(n-1)*3^(1+Ilog(3, n))+n: n in [1..20]]; // Vincenzo Librandi, Dec 30 2012 CROSSREFS Concatenation of first n numbers in other bases: 2: A047778, 3: this sequence, 4: A048436, 5: A048437, 6: A048438, 7: A048439, 8: A048440, 9: A048441, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447. Sequence in context: A268736 A247769 A116431 * A293102 A023999 A126224 Adjacent sequences:  A048432 A048433 A048434 * A048436 A048437 A048438 KEYWORD nonn,base,easy AUTHOR Patrick De Geest, May 15 1999 STATUS approved

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Last modified February 19 22:36 EST 2020. Contains 332061 sequences. (Running on oeis4.)