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 A068186 a(n) is the largest number whose product of decimal digits equals n^n. 3
 22, 333, 22222222, 55555, 333333222222, 7777777, 222222222222222222222222, 333333333333333333, 55555555552222222222, 0, 333333333333222222222222222222222222, 0, 7777777777777722222222222222 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS No digit=1 is permitted to avoid infinite number of solutions; a(n)=0 if A067734(n^n)=0. LINKS Chai Wah Wu, Table of n, a(n) for n = 2..100 FORMULA a(n) is obtained as prime factors of n^n concatenated in order of magnitude and with repetitions; a(n)=0 if n has p > 7 prime factors. EXAMPLE n=10, 10^10=10000000000, a(5)=55555555552222222222. PROG (Python) from sympy import factorint def A068186(n):     if n == 1:         return 1     pf = factorint(n)     ps = sorted(pf.keys(), reverse=True)     if ps[0] > 7:         return 0     s = ''     for p in ps:         s += str(p)*(n*pf[p])     return int(s) # Chai Wah Wu, Aug 12 2017 CROSSREFS Cf. A000312, A001222, A002473, A067734, A068183-A068187, A068189-A068191. Sequence in context: A000461 A216730 A048795 * A021284 A019623 A021794 Adjacent sequences:  A068183 A068184 A068185 * A068187 A068188 A068189 KEYWORD base,nonn AUTHOR Labos Elemer, Feb 19 2002 EXTENSIONS a(12) corrected by Chai Wah Wu, Aug 12 2017 STATUS approved

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Last modified April 13 13:24 EDT 2021. Contains 342936 sequences. (Running on oeis4.)