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A043262
Sum of digits of n-th base 3 palindrome.
1
0, 1, 2, 2, 4, 2, 3, 4, 4, 5, 6, 2, 4, 6, 4, 6, 8, 2, 3, 4, 4, 5, 6, 6, 7, 8, 4, 5, 6, 6, 7, 8, 8, 9, 10, 2, 4, 6, 4, 6, 8, 6, 8, 10, 4, 6, 8, 6, 8, 10, 8, 10, 12, 2, 3, 4, 4, 5, 6, 6, 7, 8, 4, 5, 6, 6, 7, 8, 8, 9, 10, 6, 7, 8, 8, 9, 10, 10, 11, 12, 4, 5, 6, 6, 7, 8
OFFSET
1,3
MATHEMATICA
Total/@Select[IntegerDigits[Range[0, 2000], 3], #==Reverse[#]&] (* Harvey P. Dale, Aug 08 2019 *)
PROG
(Python)
from gmpy2 import digits
def A043262(n):
if n == 1: return 0
y = 3*(x:=3**(len(digits(n>>1, 3))-1))
return int((s:=digits(n-x, 3))[-1])+(sum(int(d) for d in s[:-1])<<1) if n<x+y else sum(map(int, digits(n-y, 3)))<<1 # Chai Wah Wu, Jul 24 2024
CROSSREFS
Cf. A014190 (base 3 palindromes)
Sequence in context: A103274 A046820 A356878 * A130860 A161535 A138785
KEYWORD
nonn,base
STATUS
approved