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A033478 3x+1 sequence beginning at 3. 23
3, 10, 5, 16, 8, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1, 4, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
REFERENCES
C. A. Pickover, The Math Book, Sterling, NY, 2009; see p. 374.
LINKS
FORMULA
From Colin Barker, Oct 04 2019: (Start)
G.f.: (3 + 10*x + 5*x^2 + 13*x^3 - 2*x^4 - x^5 - 14*x^6 - 7*x^7) / ((1 - x)*(1 + x + x^2)).
a(n) = a(n-3) for n>7.
(End)
MAPLE
f:=proc(n) if n mod 2 = 0 then n/2 else 3*n+1; fi; end; g:=proc(n) local i, t1; t1:=[n]; for i from 1 to 120 do t1:=[op(t1), f(t1[nops(t1)])]; od; t1; end; g(3);
MATHEMATICA
A033478list[nmax_]:=PadRight[{3, 10, 5, 16, 8}, nmax+1, {2, 1, 4}]; A033478list[100] (* Paolo Xausa, May 31 2023 *)
PROG
(PARI) a(n)=if(n>4, [2, 1, 4][n%3+1], [3, 10, 5, 16, 8][n+1]) \\ Charles R Greathouse IV, Jun 22 2016
(PARI) Vec((3 + 10*x + 5*x^2 + 13*x^3 - 2*x^4 - x^5 - 14*x^6 - 7*x^7) / ((1 - x)*(1 + x + x^2)) + O(x^80)) \\ Colin Barker, Oct 04 2019
CROSSREFS
Row 3 of A347270.
Sequence in context: A247034 A275511 A035411 * A285576 A246777 A111127
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified March 18 22:34 EDT 2024. Contains 370951 sequences. (Running on oeis4.)