A387822 Greater of a pair of amicable numbers k < m such that A033634(k) = m and A033634(m) = k.

4, 5778432, 468052992, 1648823040

Offset

1,1

Comments

The terms are ordered according to their lesser counterparts (A387821).

Links

Table of n, a(n) for n=1..4.

Formula

a(n) = A033634(A387821(n)).

Mathematica

f[p_, e_] := 1 + (p^(e + If[OddQ[e], 2, 1]) - p)/(p^2-1); s[n_] := Times @@ f @@@ FactorInteger[n]; s[1] = 1;
seq[lim_] := Module[{sq = {}, m}, Do[m = s[n]; If[m > n && s[m] == n, AppendTo[sq, m]], {n, 1, lim}]; sq]; seq[6*10^6]

Prog

(PARI) s(n) = {my(f = factor(n), p = f[, 1], e = f[, 2]); prod(i = 1, #p, 1 + (p[i]^if(e[i] % 2, e[i]+2, e[i]+1) - p[i])/(p[i]^2 - 1)); }
list(lim) = {my(m); for(n = 1, lim, m = s(n); if(m > n && s(m) == n, print1(m, ", "))); }

Crossrefs

Cf. A033634, A325848, A387820, A387821.

Sequence in context: A204041 A065248 A116141 * A225876 A067508 A034250

Adjacent sequences: A387819 A387820 A387821 * A387823 A387824 A387825

Keyword

nonn,hard,more

Author

Amiram Eldar, Sep 09 2025

Status

approved