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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; internal format)
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OFFSET
| 0,1
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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)= -9 + Sum_{k=0..n}{(1/36)*(-59*(k mod 9)+13*((k+1) mod 9)-23*((k+2) mod 9)+13*((k+3) mod 9)+13*((k+4) mod 9)+13*((k+5) mod 9)-23*((k+6) mod 9)+13*((k+7) mod 9)+49*((k+8) mod 9)},with n>=0 - Paolo P. Lava (paoloplava(AT)gmail.com), Dec 03 2007
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CROSSREFS
| Sequence in context: A021692 A107793 A196402 * A170929 A019836 A020503
Adjacent sequences: A004490 A004491 A004492 * A004494 A004495 A004496
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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