%I #7 Apr 15 2024 14:58:26
%S 1,0,1,1,2,3,6,6,16,21,42,63,129,201,404,685,1340,2385,4625,8487,
%T 16409,30735,59282,112530,217182,415605,803076,1545463,2990945,
%U 5778267,11201472,21702645,42140890,81830744,159139428,309590883,602935713,1174779207,2290915478,4469734225,8726815041,17047041429,33319598126
%N Number of different closest packings of equal spheres for hexagonal crystals having repeat period n.
%H J. E. Iglesias, <a href="https://doi.org/10.1524/zkri.1981.155.1-2.121">A formula for the number of closest packings of equal spheres having a given repeat period</a>, Z. Krist. 155 (1981) 121-127, Table 1.
%F a(n) + A371992(n) = A000046(n).
%Y Cf. A000046, A371992.
%K nonn
%O 2,5
%A _R. J. Mathar_, Apr 15 2024