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 A219543 #21 Jan 11 2016 03:11:44 %S A219543 30,66,138,282,354,498,642,1002,1074,1362,1434,1578,2082,2154,2298, %T A219543 2478,2658,2730,2802,2874,3018,3378,3486,3522,3882,3954,4314,4494, %U A219543 4962,5034,5178,5322,5898,6114,7122,7338,7518,7554,7590,7698,7842,7914,8202,8634,8922 %N A219543 Denominators of Bernoulli numbers which are congruent to 3 (mod 9). %C A219543 The sequence contains the elements of A090801 which are == 3 (mod 9). %C A219543 Conjecture: all the first differences 36, 72, 144, 72,... of the sequence are multiples of 36. %C A219543 The conjecture is true, since elements of A090801 are 2 mod 4. - _Charles R Greathouse IV_, Nov 22 2012 %H A219543 Charles R Greathouse IV, <a href="/A219543/b219543.txt">Table of n, a(n) for n = 1..10000</a> %t A219543 listLength = 50; n0 = 10*listLength; Clear[f]; f[n_] := f[n] = Union[Reap[ For[k = 4, k <= n, k = k+2, b = Denominator[BernoulliB[k]]; If[Mod[b, 36] == 30, Sow[b]]]][[2, 1]]][[1 ;; listLength]]; f[n0]; f[n = 2 n0]; While[ Print["n = ", n]; f[n] != f[n/2], n = 2 n]; A219543 = f[n] (* _Jean-François Alcover_, Jan 11 2016 *) %o A219543 (PARI) is(n)=if(n%36-30, 0, my(f=factor(n)); if(vecmax(f[, 2])>1, return(0)); fordiv(lcm(apply(k->k-1, f[, 1])), k, if(isprime(k+1) && n%(k+1), return(0))); 1) \\ _Charles R Greathouse IV_, Nov 26 2012 %Y A219543 Second subset of the Bernoulli denominators A090801. The first is A218755. %K A219543 nonn %O A219543 1,1 %A A219543 _Paul Curtz_, Nov 22 2012