OFFSET
1,1
COMMENTS
EXAMPLE
sigma(15063) / tau(15063) = sigma(15062) / tau(15062) + sigma(15064) / tau(15064); 20088 / 4 = 23976 / 8 + 32400 / 16; 5022 = 2997 + 2025.
MATHEMATICA
r[n_] := Divide @@ DivisorSigma[{1, 0}, n]; s = {}; r1 = r[1]; r2 = r[2]; Do[r3 = r[n]; If[r2 == r1 + r3, AppendTo[s, n - 1]]; r1 = r2; r2 = r3, {n, 3, 4*10^6}]; s (* Amiram Eldar, Aug 16 2021 *)
Flatten[Position[Partition[Table[DivisorSigma[1, n]/DivisorSigma[0, n], {n, 900000}], 3, 1], _?(#[[2]] == #[[1]]+#[[3]]&), 1, Heads->False]]+1 (* The program generates the first 10 terms of the sequence. *) (* Harvey P. Dale, Apr 19 2024 *)
PROG
(Magma) [m: m in [2..10^6] | (&+Divisors(m) / #Divisors(m)) eq (&+Divisors(m - 1) / #Divisors(m - 1)) + (&+Divisors(m + 1) / #Divisors(m + 1))]
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Aug 15 2021
EXTENSIONS
a(16)-a(18) from Jon E. Schoenfield, Aug 15 2021
a(19)-a(28) from Amiram Eldar, Aug 16 2021
STATUS
approved