OFFSET
0,1
COMMENTS
Note that a(60) = -1.
EXAMPLE
PROG
(PARI) f(n) = abs(2*n-sigma(n));
a(n) = my(k=1); while(f(k) != 2*n, k++); k - (2*n+1); \\ Michel Marcus, Oct 31 2017
CROSSREFS
KEYWORD
sign
AUTHOR
Omar E. Pol, Oct 30 2017
STATUS
approved