A072199 a(n)-th factorial is the smallest factorial containing exactly n 5's, or 0 if no such number exists.

7, 17, 25, 30, 37, 41, 43, 46, 75, 65, 55, 83, 74, 80, 94, 116, 91, 114, 131, 111, 115, 136, 147, 125, 128, 143, 102, 169, 152, 157, 197, 150, 165, 185, 193, 190, 206, 198, 192, 214, 236, 203, 242, 226, 205, 256, 251, 220, 270, 239, 230, 261, 286, 222, 264

Offset

1,1

Links

Table of n, a(n) for n=1..55.

Example

a(2)=17 since 17th factorial, i.e., 17!=355687428096000 contains exactly two 5's.

Mathematica

Do[k = 1; While[ Count[IntegerDigits[k! ], 5] != n, k++ ]; Print[k], {n, 1, 60}]
With[{fs=Table[{n, n!}, {n, 500}]}, Table[SelectFirst[fs, DigitCount[#[[2]], 10, 5] == k&], {k, 100}]][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 16 2018 *)

Crossrefs

Cf. A072242, A072220, A072208, A072204, A072200, A072178, A072177, A072163 & A072124.

Sequence in context: A300298 A273745 A263264 * A309231 A183897 A300186

Adjacent sequences: A072196 A072197 A072198 * A072200 A072201 A072202

Keyword

base,nonn

Author

Shyam Sunder Gupta, Jul 30 2002

Extensions

Edited and extended by Robert G. Wilson v, Jul 31 2002

Status

approved