OFFSET
1,5
COMMENTS
Notation: (-2)[n](-1)
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
6 = 11010 -> +(1)-(1)+(0)-(1)+(0) = -1 = a(6).
PROG
(PARI) negab(n)=if(n, negab(n\(-2))*10+bittest(n, 0)); \\ A039724
a(n) = my(d=Vecrev(digits(negab(n)))); sum(k=1, #d, d[k]*(-1)^(k-1)); \\ Michel Marcus, Aug 28 2019
CROSSREFS
KEYWORD
base,easy,sign
AUTHOR
Marc LeBrun, Oct 31 2001
STATUS
approved