OFFSET
0,1
COMMENTS
Conjecture: a strictly increasing sequence. - J. Lowell, Sep 10 2008
The sequence is strictly increasing because (4*n)' = 4*n + 4*n'. - David Radcliffe, Aug 19 2014
8 is the smallest integer that has a nontrivial trajectory (not going to 0 nor reduced to a fixed point as 4) under A003415, but 15 = A090636(1) has 8 as second term in its trajectory. 20 is the next larger such integer with a distinct trajectory, but has two larger predecessors, cf. A090635. - M. F. Hasler, Nov 27 2019
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 0..100
FORMULA
a(n+1) = A003415(a(n)), a(0) = 2^3 = 8.
a(n) = A090636(n+2).
A129251(a(n)) > 0. - Reinhard Zumkeller, Apr 07 2007
a(n) = 4*A129284(n). - M. F. Hasler, Nov 27 2019
MATHEMATICA
dn[0] = 0; dn[1] = 0; dn[n_?Negative] := -dn[-n]; dn[n_] := Module[{f = Transpose[FactorInteger[n]]}, If[PrimeQ[n], 1, Total[n*f[[2]]/f[[1]]]]]; s = 2^3; Join[{s}, Table[s = dn[s], {28}]] (* T. D. Noe, Mar 07 2013 *)
PROG
(Haskell)
a129150 n = a129150_list !! n
a129150_list = iterate a003415 8 -- Reinhard Zumkeller, Apr 29 2012
(PARI) A129150(n, a=8)={if(n<0, vector(-n, n, if(n>1, a=A003415(a), a)), for(n=1, n, a=A003415(a)); a)} \\ For n<0 return the vector a[0..-n-1]. - M. F. Hasler, Nov 27 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 01 2007
EXTENSIONS
a(21)-a(27) from Paolo P. Lava, Apr 16 2012
STATUS
approved