OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
Keith F. Lynch, List of all such groups through n=1000. For each group, the first two numbers specify n and the identity element, then the group elements are listed after the colon.
FORMULA
a(n) = 1 + Sum_{d|n, gcd(d, n/d)==1} A272831(d). - Andrew Howroyd, Jul 02 2018
EXAMPLE
For instance a(10) = 8 because the following are multiplicative groups mod 10: {0*} {1*} {5*} {6*} {4,6*} {2,4,6*,8} {1*,9} {1*,3,7,9}, with identity elements marked with asterisks.
CROSSREFS
KEYWORD
nonn
AUTHOR
Keith F. Lynch, Apr 30 2016
STATUS
approved