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 A091887 #11 Nov 27 2014 15:29:58
%S A091887 1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,2,2,1,1,1,1,1,1,1,2,3,1,1,2,1,1,2,
%T A091887 1,1,1,3,1,2,3,1,1,2,1,1,2,1,1,1,1,1,1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,
%U A091887 3,1,1,1,3,1,1,1,1,2,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,1,2,1,1,1
%N A091887 Irregularity index of the n-th irregular prime A000928(n).
%C A091887 See A091888 for definition.
%H A091887 T. D. Noe, <a href="/A091887/b091887.txt">Table of n, a(n) for n=1..10000</a> (from Buhler et al.)
%H A091887 J. Buhler, R. Crandall, R. Ernvall, T. Metsankyla and M. A. Shokrollahi, <a href="http://dx.doi.org/10.1006/jsco.1999.1011">Irregular Primes and Cyclotomic Invariants to 12 Million</a>, J. Symbolic Computation 31, 2001, 89-96.
%t A091887 tp=Table[p=Prime[i]; cnt=0; k=1; While[2k<=p-3, If[Mod[Numerator[BernoulliB[2k]], p]==0, cnt++ ]; k++ ]; cnt, {i, 400}]; Select[tp, #>0&]
%Y A091887 Cf. A073277 (primes having irregularity index 2), A060975 (primes having irregularity index 3), A061576 (least prime having irregularity index n), A091888 (irregularity index of prime(n)).
%K A091887 nonn
%O A091887 1,8
%A A091887 _T. D. Noe_, Feb 09 2004