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%I #18 Jun 29 2017 11:39:33
%S 1,7,14,21,28,35,42,49,49,56,63,70,77,84,91,98,98,105,112,119,126,133,
%T 140,147,147,154,161,168,175,182,189,196,196,203,210,217,224,231,238,
%U 245,245,252,259,266,273,280,287,294,294,301,308,315,322,329,336,343,343,343,350
%N Least positive integer k for which 7^n divides k!.
%D H. Ibstedt, Smarandache Primitive Numbers, Smarandache Notions Journal, Vol. 8, No. 1-2-3, 1997, 216-229.
%H T. D. Noe, <a href="/A020646/b020646.txt">Table of n, a(n) for n = 0..1000</a>
%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">Only Problems, Not Solutions!</a>
%t lpi[n_]:=Module[{k = 1, n7 = 7^n}, While[! Divisible[k!, n7], k++]; k]; Array[lpi,60,0] (* _Harvey P. Dale_, Jun 29 2017 *)
%o (PARI) a(n) = {k = 1; while (valuation(k!, 7) < n, k++); k;} \\ _Michel Marcus_, Aug 19 2013
%Y Cf. A007843, A007844, A007845.
%K nonn
%O 0,2
%A _David W. Wilson_