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A337149
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Positive integers k such that the number of steps it takes to reach 1 in the '3x+1' problem is different for all j < k.
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2
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 17, 18, 22, 24, 25, 27, 28, 31, 33, 34, 36, 39, 41, 43, 47, 48, 49, 54, 57, 62, 65, 71, 72, 73, 78, 82, 86, 91, 94, 97, 98, 103, 105, 107, 108, 111, 114, 121, 123, 124, 129, 130, 135, 137, 142, 145, 153, 155, 159
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OFFSET
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1,2
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COMMENTS
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Positive integers k such that A337144(k) = 1.
Or positive integers k such that A006577(k) != A006577(j) for all j = 1..k-1.
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LINKS
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FORMULA
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MAPLE
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collatz:= proc(n) option remember; `if`(n=1, 0,
1 + collatz(`if`(n::even, n/2, 3*n+1)))
end:
b:= proc() 0 end:
g:= proc(n) option remember; local t;
`if`(n=1, 0, g(n-1));
t:= collatz(n); b(t):= b(t)+1
end:
a:= proc(n) option remember; local k; for k
from 1+a(n-1) while g(k)>1 do od; k
end: a(0):=0:
seq(a(n), n=1..100);
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MATHEMATICA
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collatz[n_] := collatz[n] = If[n==1, 0,
1+collatz[If[EvenQ[n], n/2, 3n+1]]];
b[_] = 0;
g[n_] := g[n] = Module[{t}, If[n==1, 0, g[n-1]];
t = collatz[n]; b[t] = b[t]+1];
a[n_] := a[n] = Module[{k}, For[k = 1+a[n-1],
g[k] > 1, k++]; k]; a[0] = 0;
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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