A253092 Log_3(A133579(n)).

0, 0, 1, 0, 1, 2, 1, 2, 3, 1, 2, 3, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 5, 6, 7, 4, 5, 6, 5, 6, 7, 6, 7, 8, 6, 7, 8, 7, 8, 9, 8, 9, 10, 8, 9, 10, 9, 10, 11, 10, 11, 12, 9, 10, 11, 10, 11, 12, 11, 12, 13, 11, 12, 13, 12, 13, 14, 13, 14, 15, 13, 14, 15, 14, 15, 16

Offset: 0

Author

N. J. A. Sloane, Feb 14 2015

Keywords

• nonn

Comments

Using the definition of A133579 this amounts to a(n) = a(n-1)-valuation_3(n) if n=3k, and a(n) = a(n-1)+1 else. - M. F. Hasler, Feb 15 2015

Examples

			a(18)=a(17)-2 because 18=3^2, a(81)=a(80)-4 because 81=3^4.
		

Links

• M. F. Hasler, Table of n, a(n) for n = 0..3000

Crossrefs

Cf. A133579.

Programs

Mathematica

nxt[{n_, a_}] := {n + 1, If[CoprimeQ[a, n + 1], 3 a, a/GCD[a, n + 1]]}; Log[3,#]&/@Join[{1},Transpose[NestList[nxt,{1,1},80]][[2]]] (* Harvey P. Dale, Feb 14 2015 *)

PARI

a=-1;A253092=vector(1000,n,a+=if(n%3,1,-valuation(n,3))) \\ M. F. Hasler, Feb 15 2015