OFFSET
1,2
LINKS
Peter J. Cameron, Pallabi Manna, and Ranjit Mehatari, On finite groups whose power graph is a cograph, arXiv:2106.14217 [math.GR], 2021. See Theorem 1.3 (c) pp. 3-4.
PROG
(PARI) isor(q) = (q==1) || isprimepower(q) || (bigomega(q)==2);
isokc(e) = my(q=2^(2*e+1)); isor(q-1) && isor(q+sqrtint(2*q)+1) && isor(q-sqrtint(2*q)+1);
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Michel Marcus, Jun 29 2021
STATUS
approved