This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A279950 List of ordered pairs (x, y) from A279812. 1
 440, 568, 2368, 2420, 5240, 5848, 10040, 11128, 12464, 12736, 21488, 21712, 24570, 29190, 34592, 36832, 126040, 152168, 133856, 133984, 134190, 142290, 139230, 175266, 159500, 177460, 200970, 248310, 244530, 279630, 244736, 246304, 283328, 306352, 284620, 337460 (list; graph; refs; listen; history; text; internal format)
 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) < ... LINKS 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 Cf. A279812. Sequence in context: A092048 A296905 A279812 * A072604 A158319 A250879 Adjacent sequences:  A279947 A279948 A279949 * A279951 A279952 A279953 KEYWORD nonn AUTHOR Michel Lagneau, Dec 23 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 20 05:25 EDT 2019. Contains 326139 sequences. (Running on oeis4.)