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 A258251 Numbers n for which there exists a fixed point in the Collatz (3x+1) trajectory of n. 0
 1, 4, 5, 9, 12, 13, 22, 23, 24, 26, 32, 33, 36, 37, 38, 49, 50, 51, 56, 58, 60, 61, 72, 74, 78, 79, 80, 86, 87, 105, 123, 124, 125, 126, 127, 130, 131, 132, 133, 134, 136, 138, 140, 141, 153, 156, 157, 158, 160, 168, 170, 192, 196, 197, 198, 200, 202, 204, 205, 206, 207, 217, 224, 232, 233, 234, 241, 246, 247, 249 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that A258772(n) > 0. LINKS EXAMPLE For n = 5, the trajectory is T(5) = [5, 16, 8, 4, 2, 1]. Since the fourth term in this sequence is 4, 5 has a fixed point. So 5 is a member of this sequence. For n = 6, the trajectory is T(6) = [6, 3, 10, 5, 16, 8, 4, 2, 1]. Here, there is no fixed point and so, 6 is not a member of this sequence. PROG (PARI) Tvect(n)=v=[n]; while(n!=1, if(n%2, k=3*n+1; v=concat(v, k); n=k); if(!(n%2), k=n/2; v=concat(v, k); n=k)); v m=1; while(m<10^3, d=Tvect(m); c=0; for(i=1, #d, if(d[i]==i, print1(m, ", "); break)); m++) CROSSREFS Cf. A258772, A006370, A070165. Sequence in context: A269741 A047610 A126004 * A331086 A332020 A184801 Adjacent sequences:  A258248 A258249 A258250 * A258252 A258253 A258254 KEYWORD nonn AUTHOR Derek Orr, Jun 11 2015 STATUS approved

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Last modified July 28 06:33 EDT 2021. Contains 346317 sequences. (Running on oeis4.)