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4, 5, 3, 7, 8, 6, 1, 2, 0, 13, 14, 12, 16, 17, 15, 10, 11, 9, 22, 23, 21, 25, 26, 24, 19, 20, 18, 31, 32, 30, 34, 35, 33, 28, 29, 27, 40, 41, 39, 43, 44, 42, 37, 38, 36, 49, 50, 48, 52, 53, 51, 46, 47, 45, 58, 59, 57, 61
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,1
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,0,0,1,-1).
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FORMULA
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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.
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MATHEMATICA
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LinearRecurrence[{1, 0, 0, 0, 0, 0, 0, 0, 1, -1}, {4, 5, 3, 7, 8, 6, 1, 2, 0, 13, 14}, 80] (* Jinyuan Wang, Mar 10 2020 *)
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PROG
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(Python)
def tersum(a, b):
c, pow3 = 0, 1
while a + b > 0:
a, ra = divmod(a, 3)
b, rb = divmod(b, 3)
c, pow3 = c + pow3*((ra+rb)%3), pow3*3
return c
def a(n): return tersum(n, 4)
(PARI) my(table=[4, 4, 1, 4, 4, 1, -5, -5, -8]); a(n) = n + table[n%9+1]; \\ Kevin Ryde, Apr 05 2021
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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