A070009 - OEIS

A070009

Least number m such that the arithmetic mean of the distinct prime divisors of m is equal to 2^n.

2, 15, 39, 87, 183, 2071, 1255, 1527, 3063, 18402, 12279, 106327, 49143, 622231, 589794, 1703767, 1310695, 9961111, 3145719, 31457210, 12582903, 310377127, 50331639, 2046816631, 335544295, 10603194271, 8858369762, 1610612727, 44023413103, 40802188951

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Are there any terms with more than 3 prime factors? - David Wasserman, May 05 2003

LINKS

Table of n, a(n) for n=1..30.

FORMULA

a(n) = Min{x; A008472(x)/A001221(x)=2^n}.

EXAMPLE

a(15) = 589794 because m = 2*3*98299; mean = (2+3+98299)/3 = 32768 = 2^15.

MATHEMATICA

a = Table[0, {21}]; Do[b = Transpose[ FactorInteger[n]][[1]]; c = Log[2, Apply[ Plus, b] / Length[b]]; If[ IntegerQ[c] && a[[c]] == 0, a[[c]] = n], {n, 2, 10^8/3}]; a

CROSSREFS

Cf. A070005, A070006, A070007, A070008, A070009, A008472, A001414, A001221.

Sequence in context: A295367 A214541 A180223 * A070170 A033568 A200156

Adjacent sequences: A070006 A070007 A070008 * A070010 A070011 A070012

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 11 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Apr 30 2002

More terms from David Wasserman, May 05 2003

a(29)-a(30) from Donovan Johnson, Aug 06 2012

STATUS

approved