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 A245317 #15 Jul 22 2025 15:39:00
%S A245317 41,62,83,94,105,126,147,158,169,1810,2011,2112,2213,2414,2515,2616,
%T A245317 2717,2818,3019,3220,3321,3422,3523,3624,3825,3926,4027,4228,4429,
%U A245317 4530,4631,4832,4933,5034,5135,5236,5437,5538,5639,5740
%N A245317 Concatenate n-th composite integer with n.
%H A245317 Jens Kruse Andersen, <a href="/A245317/b245317.txt">Table of n, a(n) for n = 1..10000</a>
%e A245317 a(8)=158 since 15 is the 8th composite integer.
%t A245317 w=Select[Range[2,57],!PrimeQ[#]&];Table[FromDigits[Flatten[{IntegerDigits[w[[n]]],IntegerDigits[n]}]],{n,1,40}]
%t A245317 With[{cmps=Select[Range[100],CompositeQ]},#[[1]]10^IntegerLength[#[[2]]]+#[[2]]&/@Thread[{cmps,Range[Length[cmps]]}]] (* _Harvey P. Dale_, Jul 22 2025 *)
%Y A245317 Cf. A002808, A245315, A245316, A246808.
%K A245317 nonn,base
%O A245317 1,1
%A A245317 _Jahangeer Kholdi_, Sep 15 2014