A348343 - OEIS

A348343

Smaller 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).

336, 1792, 5376, 6096, 21504, 32004, 97536, 34062336, 64512000, 118008576, 30064771072

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OFFSET

1,1

COMMENTS

The larger counterparts are in A348344.

LINKS

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

EXAMPLE

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

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, n]], {n, 1, 10^4}]; seq

CROSSREFS

Cf. A327633, A348271, A348344.

Similar sequences: A002025, A002952, A126165, A126169, A259038, A292980, A322541, A324708.

Sequence in context: A067708 A377134 A059467 * A237862 A268807 A159206

Adjacent sequences: A348340 A348341 A348342 * A348344 A348345 A348346

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Oct 13 2021

STATUS

approved