login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A051282 2-adic valuation of A025487: largest k such that 2^k divides A025487(n), where A025487 gives products of primorials. 8
0, 1, 2, 1, 3, 2, 4, 3, 1, 5, 2, 4, 2, 6, 3, 5, 3, 7, 4, 2, 6, 1, 3, 4, 8, 5, 3, 7, 2, 4, 5, 9, 6, 4, 8, 3, 5, 2, 6, 10, 3, 7, 2, 4, 5, 9, 4, 6, 3, 7, 11, 4, 8, 1, 3, 5, 6, 10, 5, 7, 4, 8, 12, 5, 9, 2, 4, 6, 3, 7, 11, 2, 4, 6, 8, 5, 3, 9, 5, 13, 6, 10, 3, 5, 7, 4, 8, 12, 3, 5, 7, 9, 2, 6, 4, 10, 6, 14, 7, 11, 4, 6, 8, 5, 9, 13, 4, 6, 8, 3, 10, 3, 7, 1, 5, 11, 7, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) can be used for resorting A025487 and sequences indexed by A025487, e.g., A050322, A050323, A050324 and A050325.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A007814(A025487(n)) = A051903(A025487(n)). - Matthew Vandermast, Jul 03 2012

EXAMPLE

a(8) = 3 because A025487(8) = 24 and 2^3 divides 24.

MATHEMATICA

max = 40000; A025487 = {1}; lpe = {}; Do[ pe = Sort[ FactorInteger[n][[All, 2]]]; If[FreeQ[lpe, pe], AppendTo[lpe, pe]; AppendTo[A025487, n]], {n, 2, max}]; a[n_] := FactorInteger[ A025487[[n]] ][[1, 2]]; a[1] = 0; Table[a[n], {n, 1, Length[A025487]}] (* Jean-Fran├žois Alcover, Jun 14 2012, after Robert G. Wilson v *)

PROG

(Haskell)

a051282 = a007814 . a025487  -- Reinhard Zumkeller, Apr 06 2013

(PARI) isA025487(n)=my(k=valuation(n, 2), t); n>>=k; forprime(p=3, default(primelimit), t=valuation(n, p); if(t>k, return(0), k=t); if(k, n/=p^k, return(n==1)))

[valuation(n, 2) | n <- [1..1000], isA025487(n)]

\\ Or, for older versions:

apply(n->valuation(n, 2), select(isA025487, [1..1000])) \\ Charles R Greathouse IV, Nov 07 2014

CROSSREFS

A001055, A045778, A002033 and A050320.

Sequence in context: A285120 A282744 A195310 * A274121 A052306 A322886

Adjacent sequences:  A051279 A051280 A051281 * A051283 A051284 A051285

KEYWORD

nice,nonn

AUTHOR

Alford Arnold

EXTENSIONS

More terms from Naohiro Nomoto, Mar 11 2001

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 6 18:25 EDT 2020. Contains 336256 sequences. (Running on oeis4.)