OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
EXAMPLE
MATHEMATICA
f[p_, e_] := 1 - (-1)^p*(p^e); s[1] = 1; s[n_] := Abs[Times @@ (f @@@ FactorInteger[n])]; Select[Range[10^5], s[#] == s[# + 1] &]
PROG
(PARI) f(n) = sumdiv(n, d, if (gcd(d, n/d) == 1, (-1)^(d + 1) * d)); \\ A328258
isok(k) = f(k) + f(k+1) == 0; \\ Michel Marcus, Oct 24 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 24 2021
STATUS
approved