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A073500 Numbers n such that sigma(n) = sigma(n+1)+sigma(n-1). 6
954, 1300, 11142, 38214, 89484, 152154, 167784, 254136, 303280, 473316, 574716, 813920, 918080, 1307022, 2008360, 3676242, 9878244, 10368512, 12548754, 19411480, 22493262, 42413484, 77766486, 81513816, 157874000, 240828972 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson and Giovanni Resta, Table of n, a(n) for n = 1..170 (terms < 10^13, first 50 terms from Donovan Johnson)

FORMULA

a(n) = A076528(n)-1  - Alex Ratushnyak, Jul 06 2013.

MAPLE

with(numtheory); A073500:=proc(i) local n;

for n from 1 to i do

if sigma(n)=sigma(n+1)+sigma(n-1) then print(n); fi;

od; end: A073500 (10^9); # Paolo P. Lava, Apr 24 2013

MATHEMATICA

s1 = s2 = s3 = 0; Do[ s1 = s2; s2 = s3; s3 = DivisorSigma[1, n]; If[ s2 == s1 + s3, Print[n - 1]], {n, 1, 10^8}]

CROSSREFS

Cf. A000203, A076528.

Sequence in context: A096954 A048267 A251677 * A121969 A203024 A055161

Adjacent sequences:  A073497 A073498 A073499 * A073501 A073502 A073503

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Aug 27 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Oct 24 2002

a(25)-a(26) from Donovan Johnson, Feb 01 2009

STATUS

approved

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Last modified July 25 06:42 EDT 2017. Contains 289779 sequences.