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A350034
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a(n) = n/gcd(n,6) if gcd(n,6)>1, 5n + 1 otherwise.
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2
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0, 6, 1, 1, 2, 26, 1, 36, 4, 3, 5, 56, 2, 66, 7, 5, 8, 86, 3, 96, 10, 7, 11, 116, 4, 126, 13, 9, 14, 146, 5, 156, 16, 11, 17, 176, 6, 186, 19, 13, 20, 206, 7, 216, 22, 15, 23, 236, 8, 246, 25, 17, 26, 266, 9, 276, 28, 19, 29, 296, 10, 306, 31, 21, 32, 326
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OFFSET
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0,2
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COMMENTS
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The 5x+1 problem is as follows: start with any number n. If gcd(n,6)>1, divide it by gcd(n,6), otherwise multiply it by 5 and add 1. Do we always reach 1? This is an unsolved problem. It is conjectured that the answer is yes.
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,2,0,0,0,0,0,-1).
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FORMULA
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Sum_{k=1..n} a(k) ~ (23/24)*n^2. - Amiram Eldar, Oct 07 2023
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MATHEMATICA
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f[n_]:=If[GCD[n, 6]>1, n/GCD[n, 6], 5*n+1]; Table[f[n], {n, 0, 100}]
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PROG
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(PARI) a(n) = my(g = gcd(n, 6)); if (g>1, n/g, 5*n+1); \\ Michel Marcus, Dec 09 2021
(Python)
from math import gcd
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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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