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 A102838 #10 Jun 29 2024 07:17:31
%S A102838 54,250,375,686,1029,1715,2662,3993,4394,6591,6655,9317,9826,10985,
%T A102838 13718,14739,15379,20577,24167,24334,24565,34295,34391,36501,48013,
%U A102838 48778,54043,59582,60835,63869,73167,75449,85169,89167,89373
%N A102838 Composite numbers whose exponents in their canonical factorization lie in the geometric progression 1, 3, 9, ...
%H A102838 Amiram Eldar, <a href="/A102838/b102838.txt">Table of n, a(n) for n = 1..3000</a>
%e A102838 The first term having more than 2 prime powers is 105468750 = 2^1 * 3^3 * 5^9, not shown.
%t A102838 q[n_] := Module[{e = FactorInteger[n][[;;, 2]]}, Length[e] > 1 && e == 3^Range[0, Length[e]-1]]; Select[Range[10^5], q] (* _Amiram Eldar_, Jun 29 2024 *)
%o A102838 (PARI) geoprog(n,m) = { local(a,x,j,nf,fl=0); for(x=1,n, a=factor(x); nf=omega(x); for(j=1,nf, if(a[j,2]==3^(j-1),fl=1,fl=0;break); ); if(fl&nf>1,print1(x",")) ) }
%o A102838 (PARI) is(n) = if(n == 1 || isprime(n), 0, my(e = factor(n)[, 2]); for(i = 1, #e, if(e[i] != 3^(i-1), return(0))); 1); \\ _Amiram Eldar_, Jun 29 2024
%Y A102838 Cf. A102836.
%K A102838 easy,nonn
%O A102838 1,1
%A A102838 _Cino Hilliard_, Feb 27 2005