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A271623 a(0)=7; a(n) = 7*a(n-1) + 1 if a(n-1) is odd, a(n) = a(n-1)/2 otherwise. 0
7, 50, 25, 176, 88, 44, 22, 11, 78, 39, 274, 137, 960, 480, 240, 120, 60, 30, 15, 106, 53, 372, 186, 93, 652, 326, 163, 1142, 571, 3998, 1999, 13994, 6997, 48980, 24490, 12245, 85716, 42858, 21429, 150004, 75002, 37501, 262508, 131254, 65627, 459390, 229695 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Conjectured: No term of the sequence is equal to a previous term.

LINKS

Table of n, a(n) for n=0..46.

EXAMPLE

7 is odd, so it is followed by 7*7 + 1 = 50.

50 is even, so it is followed by 50/2 = 25.

MATHEMATICA

NestList[If[EvenQ[#], #/2, 7 # + 1]&, 7, 60]

PROG

(MAGMA) [n eq 1 select 7 else IsOdd(Self(n-1)) select 7*Self(n-1)+1 else Self(n-1) div 2: n in [1..60]];

(PARI) Collatz(n, lim=0) = {my(c=n, e=0, L=List(n)); if(lim==0, e=1; lim=n*10^2);

for(i=1, lim, if(c%2==0, c=c/2, c=7*c+1); listput(L, c); if(e&&c==1, break)); return(Vec(L)); }

print(Collatz(7)) \\ Adapted from A008884 \\ Altug Alkan, Apr 11 2016

CROSSREFS

Cf. A033478, A259207.

Sequence in context: A067214 A069032 A345975 * A153693 A293475 A293801

Adjacent sequences:  A271620 A271621 A271622 * A271624 A271625 A271626

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Apr 11 2016

STATUS

approved

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Last modified September 22 03:20 EDT 2021. Contains 347605 sequences. (Running on oeis4.)