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 A028328 #12 Jul 02 2025 16:01:56
%S A028328 2,4,6,8,12,10,20,30,40,14,42,70,16,56,112,140,18,72,168,252,90,240,
%T A028328 420,504,22,110,330,660,924,24,132,440,990,1584,1848,26,156,572,1430,
%U A028328 2574,3432,28,182,728,2002,4004,6006,6864,210,910,2730,10010,12870,32
%N A028328 Distinct elements in the even-Pascal triangle A028326.
%H A028328 G. C. Greubel, <a href="/A028328/b028328.txt">Table of n, a(n) for n = 0..1000</a>
%t A028328 DeleteDuplicates[Table[2*Binomial[n,k], {n,0,30}, {k,0,n}]//Flatten] (* _G. C. Greubel_, Jul 13 2024 *)
%o A028328 (SageMath)
%o A028328 A028326=flatten([[2*binomial(n,k) for k in range(n+1)] for n in range(31)])
%o A028328 def a(seq): # order preserving
%o A028328 nd = [] # no duplicates
%o A028328 [nd.append(i) for i in seq if not nd.count(i) and i%2==0]
%o A028328 return nd
%o A028328 a(A028326) # A028328 # _G. C. Greubel_, Jul 13 2024
%Y A028328 Cf. A028326, A028327, A028329, A028330, A028331, A028332.
%K A028328 nonn
%O A028328 0,1
%A A028328 _Mohammad K. Azarian_
%E A028328 More terms from _James Sellers_, Dec 08 1999