OFFSET
1,1
EXAMPLE
phi(174)=56, 175=5^2*7^1, (5+2)*(7+1)=56.
PROG
(PARI) b(n)=my(f = factor(n)); for (k=1, #f~, f[k, 1] = f[k, 1] + f[k, 2]; f[k, 2] = 1; ); factorback(f); \\ A008473
isok(k) = eulerphi(k) == b(k+1); \\ Michel Marcus, Feb 25 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Title corrected and more terms from Sean A. Irvine, Feb 24 2021
STATUS
approved