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 A129090 #17 Apr 19 2022 18:53:07
%S A129090 1,3,6,14,71,427,434,1738,15643,156431,156442,938654,12202503,
%T A129090 170835043,2562525646,20500205170,348503487891,2091020927349,
%U A129090 39729397619632,198646988098164,1390528916687151,30591636167117323,703607631843698430
%N A129090 a(1)=1; a(n) = gcd(a(n-1), n) + lcm(a(n-1), n).
%H A129090 Harvey P. Dale, <a href="/A129090/b129090.txt">Table of n, a(n) for n = 1..498</a>
%p A129090 a[1]:=1: for n from 2 to 30 do a[n]:=gcd(a[n-1],n)+lcm(a[n-1],n) od: seq(a[n],n=1..27); # _Emeric Deutsch_, Apr 13 2007
%t A129090 k = 1; Do[Print[k]; k = GCD[k, n] + LCM[k, n], {n, 2, 30}] (* _Ryan Propper_, Apr 07 2007 *)
%t A129090 nxt[{n_,a_}]:={n+1,GCD[a,n+1]+LCM[a,n+1]}; NestList[nxt,{1,1},30][[All,2]] (* _Harvey P. Dale_, Apr 19 2022 *)
%Y A129090 Cf. A129091.
%K A129090 nonn
%O A129090 1,2
%A A129090 _Leroy Quet_, Mar 29 2007
%E A129090 More terms from _Ryan Propper_ and _Emeric Deutsch_, Apr 07 2007