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 A045881 #20 Oct 28 2021 12:37:08
%S A045881 4,8,24,90,140,200,114,1832,524,888,1130,1670,2478,2972,4298,5592,
%T A045881 1328,9552,30594,19334,16142,15684,81464,28230,31908,19610,35618,
%U A045881 82074,44294,43332,34062,89690,162144,134514,173360,31398,404598,212702,188030,542604
%N A045881 Smallest of first string of exactly 2n-1 consecutive composite integers.
%H A045881 Donovan Johnson, <a href="/A045881/b045881.txt">Table of n, a(n) for n = 1..672</a> (from Nicely link)
%H A045881 Thomas R. Nicely, <a href="https://faculty.lynchburg.edu/~nicely/gaps/gaplist.html">First occurrence prime gaps</a> [For local copy see A000101]
%t A045881 Reap[For[k=2, k <= 80, k = k+2, p=3; q=5; While[q-p != k, p=q; q=NextPrime[p+1]]; Print[p+1]; Sow[p+1]]][[2, 1]] (* _Jean-François Alcover_, May 17 2013, after _Klaus Brockhaus_ *)
%t A045881 With[{cmps=Table[If[CompositeQ[n],1,0],{n,10^6}]},Flatten[Table[ SequencePosition[ cmps,Join[{0},PadRight[{},i,1],{0}],1],{i,1,81,2}],1][[All,1]]+1] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 02 2017 *)
%o A045881 (PARI) forstep(k=2,80,2,p=3;q=5;while(q-p!=k,p=q;q=nextprime(p+1));print1(p+1,",")) \\ _Klaus Brockhaus_, Jan 24 2008
%Y A045881 Equals A000230(n) + 1.
%K A045881 nonn,nice
%O A045881 1,1
%A A045881 _Erich Friedman_
%E A045881 More terms from _Harvey P. Dale_, Jul 27 2001