OFFSET
1,2
COMMENTS
The asymptotic density of this sequence is 1/2 (Erdős, 1936). - Amiram Eldar, Mar 19 2021
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Paul Erdős, On a problem of Chowla and some related problems, Mathematical Proceedings of the Cambridge Philosophical Society, Vol. 32, No. 4 (1936), pp. 530-540; alternative link.
MAPLE
with(numtheory): seq( `if`(sigma(i) < sigma(i+1), i, [][]), i=1..134);
MATHEMATICA
Select[Range[150], DivisorSigma[1, #] < DivisorSigma[1, # + 1] &] (* Carl Najafi, Aug 16 2011 *)
PROG
(Haskell)
import Data.List (elemIndices)
a053224 n = a053224_list !! (n-1)
a053224_list = map (+ 1) $ elemIndices True $
zipWith (<) a000203_list $ tail a000203_list
-- Reinhard Zumkeller, May 07 2012
(PARI) is(n)=sigma(n)<sigma(n+1) \\ Charles R Greathouse IV, Mar 09 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Asher Auel, Jan 06 2000
STATUS
approved