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 A133579 a(0)=a(1)=1; for n > 1, a(n) = 3*a(n-1) if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1), n). 7
 1, 1, 3, 1, 3, 9, 3, 9, 27, 3, 9, 27, 9, 27, 81, 27, 81, 243, 27, 81, 243, 81, 243, 729, 243, 729, 2187, 81, 243, 729, 243, 729, 2187, 729, 2187, 6561, 729, 2187, 6561, 2187, 6561, 19683, 6561, 19683, 59049, 6561, 19683, 59049, 19683, 59049, 177147 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 MAPLE f:=proc(n) option remember; if n <= 1 then 1 elif gcd(n, f(n-1))>1 then f(n-1)/gcd(n, f(n-1)) else 3*f(n-1); fi; end; [seq(f(n), n=0..50)]; # N. J. A. Sloane, Feb 14 2015 MATHEMATICA nxt[{n_, a_}]:={n+1, If[CoprimeQ[a, n+1], 3a, a/GCD[a, n+1]]}; Join[{1}, Transpose[ NestList[nxt, {1, 1}, 50]][[2]]] (* Harvey P. Dale, Feb 14 2015 *) PROG (PARI) A=vector(1000, i, 1); for(n=2, #A, A[n]=if(gcd(A[n-1], n)>1, A[n-1]/gcd(A[n-1], n), A[n-1]*3)) \\ M. F. Hasler, Feb 15 2015 CROSSREFS Cf. A133058, A133580, A253092. Sequence in context: A164308 A082511 A265307 * A088442 A037095 A160654 Adjacent sequences: A133576 A133577 A133578 * A133580 A133581 A133582 KEYWORD nonn AUTHOR Ctibor O. Zizka, Dec 26 2007 EXTENSIONS Offset, definition, and terms corrected by N. J. A. Sloane, Feb 14 2015 STATUS approved

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Last modified April 15 05:31 EDT 2024. Contains 371667 sequences. (Running on oeis4.)