OFFSET
1,1
COMMENTS
The terms of the sequence A279812 are given in increasing order. The terms of this sequence are ordered pairs (a(2n-1), a(2n)) where a(2n-1) < a(2n+1) < a(2n+3) < ...
EXAMPLE
The pair (a(1), a(2)) = (440, 568) is in the sequence because the even proper divisors of 440 are 2, 4, 8, 10, 20, 22, 40, 44, 88, 110, 220 with sum = 568 and the proper divisors of 568 are 2, 4, 8, 142, 284 with sum = 440.
MATHEMATICA
f[n_] := Total@ DeleteCases[Most@ Divisors@ n, d_ /; OddQ@ d]; DeleteCases[Union@ Table[If[# == 0, {0, 0}, Sort@ {n, # Boole[f@ # == n]}] &@ f@ n, {n, 2, 10^6}], w_ /; Or[First@ w == 0, MatchQ @@ w]] // Flatten (* Michael De Vlieger, Dec 23 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Dec 23 2016
STATUS
approved