OFFSET
0,1
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1,0,0,0,0,-1,1,0,1,-1,0,0,0,0,-1,1,0,1,-1).
FORMULA
Tersum m + n: write m and n in base 3 and add mod 3 with no carries; e.g., 5 + 8 = "21" + "22" = "10" = 1.
a(n) = A004489(n, 11). - Michel Marcus, Nov 09 2021
G.f.: (20*x^21+x^20-2*x^19-16*x^18-7*x^12+x^11-2*x^10+11*x^9-7*x^3+x^2-2*x+11) / ((x^2+x+1)*(x^18+x^9+1)*(x-1)^2). - Alois P. Heinz, Nov 09 2021
PROG
(Python)
def a(n):
k, pow3, m = 0, 1, 11
while n + m > 0:
n, rn = divmod(n, 3)
m, rm = divmod(m, 3)
k, pow3 = k + pow3*((rn+rm)%3), pow3*3
return k
print([a(n) for n in range(58)]) # Michael S. Branicky, Nov 09 2021
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved