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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).
4
448, 2032, 8128, 7168, 24384, 41984, 130048, 41940480, 102222432, 221316608, 34359738352
OFFSET
1,1
COMMENTS
The terms are ordered according to their smaller counterparts (A348343).
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
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Oct 13 2021
STATUS
approved