Voozh

A072200

a(n)-th factorial is the smallest factorial containing exactly n 6's, or 0 if no such number exists.

3, 15, 23, 26, 32, 41, 35, 45, 50, 72, 63, 83, 84, 98, 89, 94, 91, 121, 99, 142, 117, 160, 129, 0, 127, 131, 132, 154, 153, 163, 170, 179, 190, 178, 166, 189, 217, 209, 206, 174, 208, 199, 207, 211, 214, 245, 263, 175, 240, 255, 295, 234, 213, 296, 286, 266, 278

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OFFSET

1,1

COMMENTS

It is conjectured that a(24)=0 since no factorial < 10000 contained just 24 sixes.

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

a(2)=15 since the 15th factorial, i.e., 15!=1307674368000, contains exactly two 6's.

MATHEMATICA

Do[k = 1; While[ Count[IntegerDigits[k! ], 6] != n, k++ ]; Print[k], {n, 1, 60}]

CROSSREFS