A307038 -id:A307038 - cp's OEIS frontend

A307051 Lesser of amicable numbers pair m < n such that A307037(m) = n and A307037(n) = m.

4, 16, 68, 256, 1028, 4112, 7200, 65536, 262148, 921600, 1036800, 1048592, 16777472, 88218000, 371404800, 418535784576

Offset: 1

Amiram Eldar, Mar 21 2019

The larger counterparts are in A307052.
Includes all the pairs of the form {F(k)-1, F(k)} with 0 < k, where F(k) = 2^(2^k) + 1, the k-th Fermat number, is prime.
Includes all the pairs of the form {(F(k)-1)*F(m), F(k)*(F(m)-1)} with 0 < k < m, where both F(k) and F(m) are primes.
a(17) > 4*10^12. - Giovanni Resta, Mar 24 2019

Cf. A000215, A307037, A307038, A307052.

f[p_, e_] := p^e + (-1)^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; s={}; Do[m = a[n]; If[m > n && a[m] == n, AppendTo[s, n]], {n, 1, 10^7}]; s

a(16) from Giovanni Resta, Mar 24 2019

A307052 Larger of amicable numbers pair m < n such that A307037(m) = n and A307037(n) = m.

Original entry on oeis.org

5, 17, 80, 257, 1280, 4352, 8060, 65537, 327680, 1065220, 1089452, 1114112, 16842752, 100340800, 383479200, 466344000000

Offset: 1

Amiram Eldar, Mar 21 2019

The terms are ordered according to their lesser counterparts (A307051).

a(17) > 4*10^12. - Giovanni Resta, Mar 24 2019

Cf. A307037, A307038, A307051.

f[p_, e_] := p^e + (-1)^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; s={}; Do[m = a[n]; If[m > n && a[m] == n, AppendTo[s, m]], {n, 1, 10^7}]; s

a(16) from Giovanni Resta, Mar 24 2019

cp's OEIS Frontend

A307051 Lesser of amicable numbers pair m < n such that A307037(m) = n and A307037(n) = m.

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