OFFSET
1,2
COMMENTS
a(n) <= 2^n. - Robert G. Wilson v, Jul 14 2014
a(n) = 2^n iff n is a prime or n equals 4 or 6. - Robert G. Wilson v, Jul 19 2014
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..10000 (first 1000 terms from T. D. Noe)
MATHEMATICA
f[n_, i_] := f[n, i] = Block[{d, b, p, x}, p = Prime[i]; b = p^n; d = Divisors[n]; For[j = Length[d], j > 1, j--, x = d[[j]]; b = Min[b, p^x*f[n/x, i + 1]]]; b]; f[1, 1] = 1; Array[ f[#, 1] &, 42] (* Robert G. Wilson v, Jul 17 2014, after David Wasserman's PARI program below *)
PROG
(PARI) f(n, i) = local(d, best, p, x); p = prime(i); best = p^n; d = divisors(n); for (j = 2, length(d) - 1, x = d[j]; best = min(best, p^x*f(n/x, i + 1))); best; a(n) = f(n, 1) \\ David Wasserman, Feb 07 2005
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Jul 10 2003
EXTENSIONS
More terms from David Wasserman, Feb 07 2005
STATUS
approved