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 A030655 #30 Jul 04 2025 18:42:01
%S A030655 12,34,56,78,910,1112,1314,1516,1718,1920,2122,2324,2526,2728,2930,
%T A030655 3132,3334,3536,3738,3940,4142,4344,4546,4748,4950,5152,5354,5556,
%U A030655 5758,5960,6162,6364,6566,6768,6970,7172,7374,7576,7778,7980,8182,8384,8586
%N A030655 Pair up the numbers.
%C A030655 That is, a(n) is the concatenation of 2n-1 and 2n. - _Charles R Greathouse IV_, Aug 07 2012
%H A030655 Vincenzo Librandi, <a href="/A030655/b030655.txt">Table of n, a(n) for n = 1..1000</a>
%t A030655 FromDigits[Flatten[IntegerDigits/@{#}]]&/@Partition[Range[90],2] (* _Harvey P. Dale_, Sep 28 2011 *)
%o A030655 (Magma) [Seqint(Intseq(n+1) cat Intseq(n)): n in [1..86 by 2]]; // _Bruno Berselli_, Jun 18 2011
%o A030655 (PARI) a(n)=eval(concat(Str(2*n-1),2*n)) \\ _Charles R Greathouse IV_, Jun 18 2011
%Y A030655 Cf. A030656.
%Y A030655 Subsequence of A005843.
%K A030655 base,nonn,easy
%O A030655 1,1
%A A030655 _Maghraoui Abdelkader_
%E A030655 More terms from _Erich Friedman_.