OFFSET
0,3
COMMENTS
a(20)=12, a(21)=98, a(22)=26, a(23)=1, a(24)=15, a(25)=8. - Jud McCranie, Jan 19 2020
a(19) > 10^13, if it exists. - Giovanni Resta, Jan 23 2020
EXAMPLE
For n=6, a(6)=10 because phi(10+6)=8 which divides sigma(10)+6=24, and k=10 is the smallest integer with that property. - Jud McCranie, Jan 19 2020
PROG
(PARI) a(n) = k=1; while ((sigma(k)+n) % eulerphi(k+n), k++); k; \\ Michel Marcus, Feb 03 2014
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
STATUS
approved