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A281265 Variation on betrothed numbers. 0
6160, 11697, 12220, 16005, 23500, 28917, 68908, 76245, 249424, 339825, 425500, 434784, 570405, 649990, 660825, 678376, 697851, 871585, 1017856, 1077336, 1238380, 1252216, 1340865, 1483785, 1568260, 1754536, 1823925, 1899261, 2067625, 2166136, 2362360, 2479065 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Members of a pair (x,y) such that sigma(x) = sigma(y) = x + y - 1, where sigma = A000203.

The first time a pair ordered by its first element is not adjacent is x = 425500, y = 570405 which correspond to a(11) and a(13), respectively.

LINKS

Table of n, a(n) for n=1..32.

FORMULA

A007992 U A015630.

EXAMPLE

sigma(6160) = sigma(11697) = 6160 + 11697 - 1 = 17856.

MAPLE

with(numtheory): P:=proc(q) local a, b, n; for n from 1 to q do

a:=sigma(n)-n+1; b:=sigma(a)-a+1; if b=n and a<>b then print(n);

fi; od; end: P(10^9);

CROSSREFS

Cf. A000203, A005276, A007992, A015630.

Sequence in context: A203982 A204626 A318251 * A007992 A033288 A266586

Adjacent sequences:  A281262 A281263 A281264 * A281266 A281267 A281268

KEYWORD

nonn,easy

AUTHOR

Paolo P. Lava, Apr 13 2017

STATUS

approved

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Last modified December 4 13:29 EST 2021. Contains 349526 sequences. (Running on oeis4.)