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 A152670 #16 Oct 19 2024 08:34:06 %S A152670 2,14,42,132,1430,4862,16796,58786,208012,742900,2674440,35357670, %T A152670 129644790,477638700,1767263190,6564120420,24466267020,91482563640, %U A152670 343059613650,1289904147324,4861946401452,18367353072152,69533550916004 %N A152670 Even Catalan numbers. %H A152670 G. C. Greubel, <a href="/A152670/b152670.txt">Table of n, a(n) for n = 1..541</a> [duplicated terms at n=343 and n=393 removed by _Georg Fischer_, Oct 19 2024] %t A152670 Select[CatalanNumber[Range[30]], EvenQ] (* _Vladimir Reshetnikov_, Nov 02 2015 *) %o A152670 (PARI) lista(nn) = for (n=1, nn, if (((c=binomial(2*n,n)/(n+1)) % 2) == 0, print1(c, ", "))); \\ _Michel Marcus_, Nov 02 2015 %Y A152670 Cf. A000108, A038003, A152671. %K A152670 easy,nonn %O A152670 1,1 %A A152670 _Omar E. Pol_, Dec 10 2008