OFFSET
1,1
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 1..4000
EXAMPLE
22 is a term because 22 = phi(23) and 22^2 = 484 is not a totient.
83^2 * 2^k is a term for 5 < k < 34.
MAPLE
N:= 1000: # to get all terms <= N
M:= fsolve(n/(exp(gamma)*log(log(n))+3/log(log(n))) = N, n=4..N^2):
Totients:= select(`<=`, {seq(numtheory:-phi(n), n=1..M)}, N):
R:= select(t -> numtheory:-invphi(t^2) = [], Totients):
sort(convert(R, list));
PROG
(PARI) lista(nn) = {for(n=1, nn, if(istotient(n) && !istotient(n^2), print1(n, ", "))); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel and Altug Alkan, Jan 16 2017
STATUS
approved