cp's OEIS Frontend

A020902 Number of nonisomorphic cyclic subgroups of alternating group A_n (or number of distinct orders of even permutations of n objects); number of different LCM's of partitions of n which have even number of even parts.

%I A020902 #10 Apr 01 2018 20:30:00
%S A020902 1,1,1,2,3,4,5,7,8,11,13,16,18,22,26,30,35,39,46,51,60,67,76,84,94,
%T A020902 105,119,133,147,162,176,196,218,240,263,286,310,340,374,409,441,476,
%U A020902 515,559,608,662,711,762,817,883,955,1030,1104,1177,1257,1352,1453,1559
%N A020902 Number of nonisomorphic cyclic subgroups of alternating group A_n (or number of distinct orders of even permutations of n objects); number of different LCM's of partitions of n which have even number of even parts.
%D A020902 V. Jovovic, Some combinatorial characteristics of symmetric and alternating groups (in Russian), Belgrade, 1980, unpublished.
%F A020902 a(n) = A009490(n-2) + A035942(n-1) + A035942(n), n > 1, a(0)=a(1)=1.
%e A020902 a(8)=8 because lcm{1^8} = 1, lcm{1^4 * 2^2, 2^4} = 2, lcm{1^5 * 3^1, 1^2 * 3^2} = 3, lcm{4^2, 1^2 * 2^1 * 4^1} = 4, lcm{1^3 * 5^1} = 5, lcm{2^1 * 6^1, 1^1 * 2^2 * 3^1} = 6, lcm{1^1 * 7^1} = 7, lcm{3^1 * 5^1} = 15.
%Y A020902 Cf. A034891.
%K A020902 nonn
%O A020902 0,4
%A A020902 _Vladeta Jovovic_