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A279950 List of ordered pairs (x, y) from A279812. 1

%I

%S 440,568,2368,2420,5240,5848,10040,11128,12464,12736,21488,21712,

%T 24570,29190,34592,36832,126040,152168,133856,133984,134190,142290,

%U 139230,175266,159500,177460,200970,248310,244530,279630,244736,246304,283328,306352,284620,337460

%N List of ordered pairs (x, y) from A279812.

%C 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) < ...

%e 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.

%t 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 *)

%Y Cf. A279812.

%K nonn

%O 1,1

%A _Michel Lagneau_, Dec 23 2016

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Last modified December 3 02:56 EST 2020. Contains 338899 sequences. (Running on oeis4.)