A332976 Solutions k of the equation s(k) = s(k-1) + s(k-2) where s(k) = isigma(k) - k is the sum of proper infinitary divisors of k (A126168).

3, 8, 10, 21, 3237, 7377, 146139, 584835, 9988999095, 25997557299

Offset

1,1

Links

Table of n, a(n) for n=1..10.

Example

8 is a term since s(8) = 7 and s(6) + s(7) = 6 + 1 = 7.

Mathematica

fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ fun @@@ FactorInteger[n]; s[n_] := isigma[n] - n; Select[Range[3, 6*10^5], s[#] == s[# - 1] + s[# - 2] &]

Crossrefs

The infinitary version of A291176.

Cf. A065557, A065900, A075565, A076136, A076251, A126168, A145469, A291126, A292033, A294995, A332975.

Sequence in context: A353078 A131725 A346370 * A032914 A088072 A213033

Adjacent sequences: A332973 A332974 A332975 * A332977 A332978 A332979

Keyword

nonn,more

Author

Amiram Eldar, Mar 04 2020

Status

approved