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 A030656 #43 Sep 08 2022 08:44:50 %S A030656 1,23,45,67,89,1011,1213,1415,1617,1819,2021,2223,2425,2627,2829,3031, %T A030656 3233,3435,3637,3839,4041,4243,4445,4647,4849,5051,5253,5455,5657, %U A030656 5859,6061,6263,6465,6667,6869,7071,7273,7475,7677,7879,8081,8283,8485,8687,8889 %N A030656 Pair up the numbers. %H A030656 Michel Marcus, <a href="/A030656/b030656.txt">Table of n, a(n) for n = 0..5000</a> %t A030656 seq[n_] := FromDigits[Flatten[IntegerDigits /@ #]] & /@ Partition[Range[0, (n + 1)*2], 2]; %t A030656 seq[44] (* _Harvey P. Dale_, Jan 24 2012, edited by _Robert P. P. McKone_, Jan 23 2021 *) %o A030656 (Magma) [Seqint(Intseq(n+1) cat Intseq(n)): n in [0..86 by 2]]; // _Bruno Berselli_, Jun 18 2011 %o A030656 (PARI) a(n)=eval(Str(2*n,2*n+1)) \\ _Charles R Greathouse IV_, Jul 21 2016 %o A030656 (Python) %o A030656 def a(n): return int(str(2*n)+str(2*n+1)) %o A030656 print([a(n) for n in range(45)]) # _Michael S. Branicky_, Jan 23 2021 %Y A030656 Cf. A030655. %Y A030656 Subsequence of A005408. %K A030656 base,nonn,easy %O A030656 0,2 %A A030656 _Maghraoui Abdelkader_ %E A030656 More terms from _Erich Friedman_