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A354170
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Odd numbers whose Collatz trajectory includes 11 odd numbers.
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0
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57, 59, 115, 119, 229, 237, 461, 465, 473, 477, 507, 513, 917, 931, 943, 945, 947, 949, 971, 987, 1015, 1025, 1027, 1031, 1129, 1131, 1845, 1857, 1861, 1867, 1881, 1887, 1891, 1893, 1905, 1909, 1943, 1945, 1953, 1975, 2029, 2051, 2053, 2055, 2059, 2063, 2073
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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119 is a term since its Collatz trajectory is 119, 358, 179, 538, 269, 808, 404, 202, 101, 304, 152, 76, 38, 19, 58, 29, 88, 44, 22, 11, 34, 17, 52, 26, 13, 40, 29, 10, 5, 16, 8, 4, 2, 1, which has 11 odd numbers.
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MAPLE
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b:= proc(n) option remember; irem(n, 2, 'r')+
`if`(n=1, 0, b(`if`(n::odd, 3*n+1, r)))
end:
q:= n-> is(n::odd and b(n)=11):
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MATHEMATICA
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q[n_] := Count[NestWhileList[If[OddQ[#], 3 # + 1, #/2] &, n, # > 1 &], _?OddQ] == 11; Select[2*Range[1000] - 1, q] (* Amiram Eldar, May 18 2022 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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