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 A070975 Number of steps to reach 1 in `3x+1' (or Collatz) problem starting with prime(n). 5
 1, 7, 5, 16, 14, 9, 12, 20, 15, 18, 106, 21, 109, 29, 104, 11, 32, 19, 27, 102, 115, 35, 110, 30, 118, 25, 87, 100, 113, 12, 46, 28, 90, 41, 23, 15, 36, 23, 67, 31, 31, 18, 44, 119, 26, 119, 39, 70, 13, 34, 83, 52, 21, 65, 122, 78, 29, 42, 16, 42, 60, 117, 37, 86, 130, 37, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS T. D. Noe, Table of n, a(n) for n=1..10000 FORMULA a(n) = A006577(prime(n)). - Michel Marcus, Sep 07 2014 MATHEMATICA ns[n_]:=Length[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #!=1&]]-1; ns/@ Prime[Range[70]] (* Harvey P. Dale, Jul 29 2014 *) PROG (PARI) for(n=2, 100, s=prime(n); t=0; while(s!=1, t++; if(s%2==0, s=s/2, s=3*s+1); if(s==1, print1(t, ", "); ); )) (Python) from sympy import prime def a006577(n): if n==1: return 0 x=0 while True: if n%2==0: n//=2 else: n = 3*n + 1 x+=1 if n<2: break return x def a(n): return a006577(prime(n)) print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Jun 05 2017 CROSSREFS Cf. A006577. Sequence in context: A299556 A282978 A125719 * A265763 A064024 A284085 Adjacent sequences: A070972 A070973 A070974 * A070976 A070977 A070978 KEYWORD easy,nonn AUTHOR Benoit Cloitre, May 17 2002 STATUS approved

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Last modified August 3 21:27 EDT 2024. Contains 374905 sequences. (Running on oeis4.)