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 A038482 #16 Apr 05 2025 17:17:15
%S A038482 57,351,393,399,2409,2451,2457,2745,2751,2793,16815,16857,16863,17151,
%T A038482 17157,17199,19209,19215,19257,19551,117657,117699,117705,117993,
%U A038482 117999,118041,120051,120057,120099,120393,134457,134463,134505,134799,136857,823551,823593
%N A038482 Sums of 3 distinct powers of 7.
%H A038482 Amiram Eldar, <a href="/A038482/b038482.txt">Table of n, a(n) for n = 1..10000</a>
%t A038482 Union[Total/@Subsets[7^Range[0,10],{3}]] (* _Harvey P. Dale_, May 06 2014 *)
%o A038482 (Python)
%o A038482 from math import isqrt, comb
%o A038482 from sympy import integer_nthroot
%o A038482 def A038482(n): return 7**((r:=n-1-comb((m:=integer_nthroot(6*n,3)[0])+(t:=(n>comb(m+2,3)))+1,3))-comb((k:=isqrt(b:=r+1<<1))+(b>k*(k+1)),2))+7**((a:=isqrt(s:=n-comb(m-(t^1)+2,3)<<1))+((s<<2)>(a<<2)*(a+1)+1))+7**(m+t+1) # _Chai Wah Wu_, Apr 05 2025
%Y A038482 Base-7 interpretation of A038445.
%Y A038482 Cf. A000420, A038481, A038483.
%K A038482 nonn,easy
%O A038482 1,1
%A A038482 _Olivier Gérard_
%E A038482 Offset corrected by _Amiram Eldar_, Jul 14 2022