OFFSET
1,2
COMMENTS
Contains all even n >= 2, no primes, all prime powers p^n, for n>1. Other entries are complicated and follow from certain congruences.
REFERENCES
Aine NiShe, Commutativity and Generalizations in Finite Groups, Ph.D.thesis in preparation.
EXAMPLE
a(1)=1,since |G/Z(G)|=1 for all Abelian groups G; a(2)=4,since |Q/Z(Q)|=4 where Q is the quaternion group of order eight.
CROSSREFS
KEYWORD
nonn,nice,more
AUTHOR
STATUS
approved