OFFSET
1,1
COMMENTS
It's often the case that the sum of divisors for an odd number is less than at least one of its adjacent even numbers. This sequence lists the exceptions.
Most terms are congruent to 3 modulo 6. It seems that the smallest term not congruent to 3 modulo 6 is greater than 10^12.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..10000
EXAMPLE
sigma(314) = 474, sigma(315) = 624, sigma(316) = 560, so 315 is a term.
MATHEMATICA
Select[Range[1, 8000, 2], DivisorSigma[1, #] > DivisorSigma[1, (#+1)] && DivisorSigma[1, #] > DivisorSigma[1, (#-1)] &] (* K. D. Bajpai, Nov 19 2019 *)
PROG
(PARI) forstep(n=3, 2000, 2, if(sigma(n)>sigma(n-1)&&sigma(n)>sigma(n+1), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jianing Song, Jan 12 2019
STATUS
approved