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%I #13 Aug 27 2022 08:14:06
%S 18,55,83,125,47,71,107,161,121,91,137,103,155,233,175,263,395,593,
%T 445,167,251,377,283,425,319,479,719,1079,1619,2429,911,1367,2051,
%U 3077,577,433,325,61,23,35,53,5,1
%N a(0)=18; a(n+1) = largest odd factor of 3*a(n)+1; stop when a(n)=1.
%C Similar to a Collatz sequence.
%F a(n+1) = A000265(3*a(n)+1). - _Michel Marcus_, Aug 23 2022
%e a(4)=47 because (a(3)*3+1)/2^3 = 47.
%o (PARI) f(n) = n >> valuation(n, 2); \\ A000265
%o lista(nn) = my(list=List(), x = 18, i=0); while (1, listput(list, x); x = f(3*x+1); i++; if (i>100, break)); Vec(list); \\ _Michel Marcus_, Aug 23 2022
%Y Cf. A000265.
%K easy,nonn,fini,full
%O 0,1
%A Mitch Cervinka (puritan(AT)planetkc.com), Nov 20 2003
%E Edited by _Don Reble_, Nov 08 2005
%E Corrected by _Doug Unger_, Aug 26 2022
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