OFFSET
1,4
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..55
EXAMPLE
a(2) = 1/(1/phi(3)+1/phi(6)) = 1/(1/2+1/2) = 1.
a(3) = 1/(1/phi(4)+1/phi(8)+1/phi(12)) = 1/(1/2+1/4+1/4) = 1.
a(4) = 1/(1/phi(7)+1/phi(14)+1/phi(21)+1/phi(28)) = 1/(1/6+1/6+1/12+1/12) = 2.
PROG
(PARI) a(n) = my(k=1); while (denominator(m=1/sum(j=1, n, 1/eulerphi(k*j))) != 1, k++); m;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 20 2021
STATUS
approved