A134716 - OEIS

%I #12 Mar 31 2012 13:22:05

%S 1,2,12,180,27720,122522400,130429015516800,1970992304700453905270400,

%T 1897544233056092162003806758651798777216000,

%U 4368924363354820808981210203132513655327781713900627249499856876120704000

%N a(n) = least number m such that sigma(m)/m > n, where sigma(m) = sum of divisors of m.

%e Values written as products of primorials:

%e n a(n)

%e 0 1

%e 1 2

%e 2 2*3#

%e 3 3#*5# (= 180)

%e 4 2*3#*11#

%e 5 8*5#*17#

%e 6 16*3#*7#*29#

%e 7 8*3#*3#*7#*53#

%e 8 32*3#*3#*5#*11#*89#

%e 9 32*3#*3#*7#*17#*157#

%e 10 16*3#*3#*5#*7#*23#*271#

%e 11 16*3#*3#*5#*7#*29#*487#

%e 12 16*3#*3#*5#*7#*13#*31#*857#

%Y Cf. A023199 (least k with sigma(k) >= nk)

%K nonn

%O 0,2

%A _Pierre CAMI_, Jan 27 2008, corrected Feb 26 2008 with the help of Emeric Deutsch

%E More terms can be obtained by expanding the expressions in the example lines. - _N. J. A. Sloane_, Feb 26 2008