OFFSET
1,2
COMMENTS
Positive integers such that for every integer m==4 (mod 9) there exists a unique representation of m as a sum of the form a(l)+3a(s).
PROG
(PARI) isa(n) = {my(d=Vecrev(digits(n, 3)), k=3); while (k <= #d, if (d[k], return (0)); k += 2; ); d[1] == 1; } \\ A146085
isok(n) = !((n+2) % 3) && isa((n+2)/3); \\ Michel Marcus, Dec 09 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Oct 27 2008
EXTENSIONS
More terms from Michel Marcus, Dec 09 2018
STATUS
approved