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A175876 Numbers n such that sigma(n+2) = 2*sigma(n). 4
118, 1558, 2938, 17758, 19918, 32218, 33838, 55963, 71038, 186778, 308038, 511498, 523774, 553498, 699358, 838213, 1048903, 1159378, 1328938, 1333246, 1700038, 2462686, 2703886, 2956078, 3115318, 3561094, 3764206, 3972694, 7625878, 7852918, 8048962 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(1) = A175874(2).

LINKS

Vincenzo Librandi and Donovan Johnson, Table of n, a(n) for n = 1..1000 (first 171 terms from Vincenzo Librandi)

MAPLE

with(numtheory); A175876:=proc(q) local n;

for n from 2 to q do if sigma(n+2)=2*sigma(n) then print(n); fi; od;  end:

A175876 (10^10); # Paolo P. Lava, Apr 04 2013

MATHEMATICA

Do[If[DivisorSigma[1, n+2]==2 DivisorSigma[1, n], Print[n]], {n, 2, 10^7}] (* or *) Select[Range[8000000], DivisorSigma[1, # + 2] == 2 DivisorSigma[1, #]&](* Vincenzo Librandi, Apr 04 2013 *)

CROSSREFS

Cf. A000203, A002961, A175874, A175875.

Sequence in context: A250793 A334646 A232776 * A220715 A230917 A230248

Adjacent sequences:  A175873 A175874 A175875 * A175877 A175878 A175879

KEYWORD

nonn

AUTHOR

Zak Seidov, Oct 06 2010

STATUS

approved

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Last modified April 14 12:11 EDT 2021. Contains 342949 sequences. (Running on oeis4.)