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a(n) = least k>1 such that k^n divides k!.
4

%I #10 Mar 30 2012 17:30:16

%S 2,6,15,18,12,32,24,36,40,45,48,100,84,60,154,165,72,96,80,126,90,135,

%T 286,200,312,264,168,120,297,189,160,330,544,210,144,224,300,385,396,

%U 324,252,680,350,180,280,748,572,486,400,405,315,528,320,336,450,512,288,240,715

%N a(n) = least k>1 such that k^n divides k!.

%C For n >= 2, least k such that A011776(k)=n.

%D Ivan Niven, Herbert S. Zuckerman and Hugh L. Montgomery, An Introduction to the Theory Of Numbers, Fifth Edition, John Wiley and Sons, Inc., NY 1991.

%D J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 251.

%H T. D. Noe, <a href="/A011777/b011777.txt">Table of n, a(n) for n=1..345</a>

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>

%Y See A133481 for a better version. Cf. A011776, A011778.

%K nonn,easy

%O 1,1

%A _Robert G. Wilson v_