A348344 - OEIS

A348344

Larger member of a noninfinitary amicable pair: numbers (k, m) such that nisigma(k) = m and nisigma(m) = k, where nisigma(k) is the sum of the noninfinitary divisors of k (A348271).

448, 2032, 8128, 7168, 24384, 41984, 130048, 41940480, 102222432, 221316608, 34359738352

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

The terms are ordered according to their smaller counterparts (A348343).

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

448 is a term since A348271(448) = 336 and A348271(336) = 448.

MATHEMATICA

f[p_, e_] := Module[{b = IntegerDigits[e, 2], m}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ f @@@ FactorInteger[n]; s[n_] := DivisorSigma[1, n] - isigma[n]; seq={}; Do[m=s[n]; If[m>n && s[m]==n, AppendTo[seq, m]], {n, 1, 10^4}]; seq

CROSSREFS

Cf. A327633, A348271, A348343.

Similar sequences: A002046, A002953, A126166, A126170, A259039, A292981, A322542, A324709.

Sequence in context: A235177 A346514 A194648 * A234438 A048632 A366815

Adjacent sequences: A348341 A348342 A348343 * A348345 A348346 A348347

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Oct 13 2021

STATUS

approved