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A274558 Numbers n such that sigma(n)==0 (mod n-6). 2
7, 13, 14, 20, 30, 45, 76, 630, 688, 2310, 8896, 133888, 537051136, 1631268870 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

sigma(7) mod (7-6) = 8 mod 1 = 0.

MAPLE

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

if n+h>0 then if type(sigma(n)/(n+h), integer) then print(n); fi; fi; od; end: P(10^9, -6);

MATHEMATICA

Select[Range[7, 10^6], Mod[DivisorSigma[1, #], # - 6] == 0 &] (* Michael De Vlieger, Jul 05 2016 *)

CROSSREFS

Cf. A045770, A067702, A088833, A181598, A274551-A274557, A274559-A274566.

Sequence in context: A072864 A232437 A275201 * A120100 A308525 A104217

Adjacent sequences:  A274555 A274556 A274557 * A274559 A274560 A274561

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Jul 05 2016

EXTENSIONS

a(13)-a(14) from Giovanni Resta

STATUS

approved

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Last modified July 12 10:20 EDT 2020. Contains 335657 sequences. (Running on oeis4.)