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 A134825 #21 Feb 27 2024 03:02:27
%S A134825 1,0,-1,0,-1,0,-1,1,-8,54,-530,6192,-86581,1425517,-27298232,
%T A134825 601580873,-15116315768,429614643061,-13711655205089,488332318973593,
%U A134825 -19296579341940069,841693047573682615,-40338071854059455414,2115074863808199160560,-120866265222965259346028
%N A134825 Floor of the even-indexed Bernoulli numbers B_{2n} = A000367(n)/A002445(n).
%D A134825 C. J. Moreno and S. S. Wagstaff, Jr., Sums of Squares of Integers, Chapman & Hall, 2006, p. 107.
%F A134825 a(n) = floor(B_(2n)), n>=0, with B_{2n} = A000367(n)/A002445(n) = A027641(2n)/A027642(2n).
%e A134825 n=4: B_8=-1/30=-0,033... hence a(4)=-1.
%t A134825 Floor@BernoulliB[2 Range[0, 20]] (* _Vladimir Reshetnikov_, Nov 12 2015 *)
%o A134825 (PARI) vector(30, n, n--; floor(bernfrac(2*n))) \\ _Altug Alkan_, Nov 12 2015
%Y A134825 Cf. A000367, A002445, A014509, A027641, A027642.
%K A134825 sign,easy
%O A134825 0,9
%A A134825 _Wolfdieter Lang_, Nov 13 2007