OFFSET
1,3
COMMENTS
LINKS
Jianing Song, Table of n, a(n) for n = 1..10000
Wikipedia, Multiplicative group of integers modulo n
EXAMPLE
The solutions to (Z/kZ)* = C_6 are k = 7, 9, 14 and 18, so a(7) = a(9) = a(14) = a(18) = 7.
The solutions to (Z/kZ)* = C_2 X C_20 are k = 55, 75, 100, 110 and 150, so a(55) = a(75) = a(100) = a(110) = a(150) = 55.
The solutions to (Z/kZ)* = C_2 X C_12 are k = 35, 39, 45, 52, 70, 78 and 90, so a(35) = a(39) = a(45) = a(52) = a(70) = a(78) = a(90) = 35.
PROG
(PARI) a(n) = my(i=eulerphi(n)); while(znstar(i)[2]!=znstar(n)[2], i++); i
CROSSREFS
KEYWORD
nonn
AUTHOR
Jianing Song, Oct 04 2018
STATUS
approved