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 A038481 #14 Apr 05 2025 15:31:52
%S A038481 8,50,56,344,350,392,2402,2408,2450,2744,16808,16814,16856,17150,
%T A038481 19208,117650,117656,117698,117992,120050,134456,823544,823550,823592,
%U A038481 823886,825944,840350,941192,5764802,5764808,5764850,5765144,5767202
%N A038481 Sums of 2 distinct powers of 7.
%H A038481 Robert Israel, <a href="/A038481/b038481.txt">Table of n, a(n) for n = 0..10010</a>
%F A038481 G.f.: ((1-x)*(1-7*x))^(-1) * (2 - 8*x + sum_{k>=0} ((1+5*7^k)*x^(k*(k+1)/2) + (1+41*7^k)*x^(1+k*(k+1)/2))). - _Robert Israel_, Feb 09 2018
%p A038481 seq(seq(7^i+7^j,j=0..i-1),i=1..10); # _Robert Israel_, Feb 09 2018
%t A038481 Sort[Total/@Subsets[7^Range[0,10],{2}]] (* _Harvey P. Dale_, Jul 29 2015 *)
%o A038481 (Python)
%o A038481 from math import isqrt
%o A038481 def A038481(n): return 7**(m:=isqrt(n<<3)+1>>1)+7**(n-1-(m*(m-1)>>1)) # _Chai Wah Wu_, Apr 05 2025
%Y A038481 Base 7 interpretation of A038444.
%K A038481 nonn,easy
%O A038481 0,1
%A A038481 _Olivier Gérard_