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 A153087 #8 Apr 05 2019 05:32:23 %S A153087 6,66,114,162,5466,1026,1926,606,5466,1746,29154,522,3838386,27066, %T A153087 4302,1254,92886,3246,2466,1578,113573466,1026,129474,9402,280201746, %U A153087 66,236646,231006,6808626,122826,545646,1422,9003546,66666,10242,2874,418384938,3344058 %N A153087 a(n) = A051717(3n) + A051717(3n+1) + A051717(3n+2). %C A153087 All terms are multiples of 6. %C A153087 The first differences are 60, 48, 48, 5304, -4440, ... Apparently (checked for the first 700 entries) these are multiples of 12. %p A153087 C:=proc(n) if n=0 then RETURN(1); fi; if n mod 2 = 0 then RETURN(bernoulli(n)+bernoulli(n-1)); else RETURN(-bernoulli(n)-bernoulli(n-1)); fi; end: %p A153087 A051717 := proc(n) denom(C(n)) ; end: A153087 := proc(n) A051717(3*n)+A051717(3*n+1)+A051717(3*n+2) ; end: seq(A153087(n),n=0..120) ; # _R. J. Mathar_, Sep 07 2009 %Y A153087 Cf. A051717, A140812. %K A153087 nonn %O A153087 0,1 %A A153087 _Paul Curtz_, Dec 18 2008 %E A153087 Extended by _R. J. Mathar_, Sep 07 2009