OFFSET
1,1
COMMENTS
The sigma() in the definition is the sum-of-divisors function A000203.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..10000
EXAMPLE
a(26)=186 because sigma(186-26)=sigma(160)=378=sigma(212)=sigma(186+26) and there is no k such that 26<k<186 for which sigma(k-26)=sigma(k+26).
MATHEMATICA
Table[Min[Select[Range[500], DivisorSigma[1, # - n] == DivisorSigma[1, # + n] && # > n &]], {n, 50}]
PROG
(PARI) a(n)={my(k=n+1); while(sigma(k-n)<>sigma(k+n), k++); k} \\ Andrew Howroyd, Feb 25 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jayanta Basu, Mar 26 2013
STATUS
approved