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Duplicate of A008621.
0

%I #8 Jun 04 2021 14:45:38

%S 1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,6,6,6,6,7,7,7,7,8,8,8,8,9,9,9,

%T 9,10,10,10,10,11,11,11,11,12,12,12,12,13,13,13,13,14,14,14,14,15,15,

%U 15,15,16,16,16,16,17,17,17,17,18,18,18,18,19,19,19,19,20,20,20,20,21,21

%N Duplicate of A008621.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GraphThickness.html">Graph Thickness</a>

%F G.f.: x(1+x^3-x^4)/((1-x)^2(1+x)(1+x^2)). - _R. J. Mathar_, Sep 12 2008

%t Ceiling[(n+1)/4]

%Y Cf. A002265, A128929.

%K dead

%O 1,4

%A _Eric W. Weisstein_, Sep 09 2008