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Numbers n such that the number of groups of order n equals the number of groups of order n + 1.
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%I #4 Jan 28 2018 18:58:21

%S 1,2,9,21,25,38,45,57,93,105,121,165,194,201,202,205,206,218,253,261,

%T 301,315,325,326,357,361,381,385,422,453,477,482,494,506,538,542,554,

%U 603,614,626,633,662,746,758,765,801,841,861,873,897,921,925,934,1005,1017

%N Numbers n such that the number of groups of order n equals the number of groups of order n + 1.

%H H. U. Besche, B. Eick and E. A. O'Brien, <a href="http://dx.doi.org/10.1142/S0218196702001115">A Millennium Project: Constructing Small Groups</a>, Internat. J. Algebra and Computation, 12 (2002), 623-644.

%H Gordon Royle, <a href="http://staffhome.ecm.uwa.edu.au/~00013890/remote/cubcay/">Numbers of Small Groups</a>

%H <a href="/index/Gre#groups">Index entries for sequences related to groups</a>

%F Sequence is { n | A000001(n+1) = A000001(n) }.

%p with(GroupTheory):

%p for n from 1 to 300 do if NumGroups(n+1) = NumGroups(n) then print(n); fi; od;

%o (GAP) Filtered([1..500], n -> NumberSmallGroups(n) = NumberSmallGroups(n+1));

%Y Cf. A000001. Numbers n having precisely k groups of orders n and n + 1: A295230 (k=2), A295990 (k=4), A295991 (k=5), A295992 (k=6), A295993 (k=8), A298427 (k=9), A (k=10), A295994 (k=11), A295995 (k=15).

%K nonn

%O 1,2

%A _Muniru A Asiru_, Jan 28 2018