This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A048438 #31 Jun 13 2025 10:49:34
%S A048438 1,8,51,310,1865,67146,2417263,87021476,3132773145,112779833230,
%T A048438 4060073996291,146162663866488,5261855899193581,189426812370968930,
%U A048438 6819365245354881495,245497148832775733836,8837897357979926418113,318164304887277351052086,11453914975941984637875115
%N A048438 Take the first n numbers written in base 6, concatenate them, then convert from base 6 to base 10.
%C A048438 The first three primes in this sequence occur for n = 11 (a(11) = 4060073996291), n = 43 (a(43) = 4.3194...*10^68), n = 173 (a(n) = 1.3014...*10^372) (email from Kurt Foster, Oct 24 2015). - _N. J. A. Sloane_, Oct 25 2015
%H A048438 Vincenzo Librandi, <a href="/A048438/b048438.txt">Table of n, a(n) for n = 1..200</a>
%e A048438 a(8) = (1)(2)(3)(4)(5)(10)(11)(12) = 12345101112_6 = 87021476.
%t A048438 If[STARTPOINT==1, n={}, n=Flatten[IntegerDigits[Range[STARTPOINT-1], 6]]]; Table[AppendTo[n, IntegerDigits[w, 6]]; n=Flatten[n]; FromDigits[n, 6], {w, STARTPOINT, ENDPOINT}] (* _Dylan Hamilton_, Aug 11 2010 *)
%t A048438 Table[FromDigits[Flatten[IntegerDigits[#,6]&/@Range[n]],6],{n,20}] (* _Harvey P. Dale_, Sep 29 2012 *)
%o A048438 (Magma) [n eq 1 select 1 else Self(n-1)*6^(1+Ilog(6, n))+n: n in [1..20]]; // _Vincenzo Librandi_, Dec 30 2012
%Y A048438 Cf. A014829.
%Y A048438 Concatenation of first n numbers in other bases: 2: A047778, 3: A048435, 4: A048436, 5: A048437, 6: this sequence, 7: A048439, 8: A048440, 9: A048441, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447.
%K A048438 nonn,base,easy
%O A048438 1,2
%A A048438 _Patrick De Geest_, May 15 1999