A202708 Sum of digits of n! divided by 9.

1, 1, 1, 3, 3, 4, 3, 3, 5, 5, 7, 7, 6, 5, 6, 7, 8, 11, 9, 8, 9, 12, 10, 14, 13, 15, 12, 16, 16, 16, 19, 17, 12, 21, 21, 16, 21, 20, 24, 23, 24, 25, 26, 25, 24, 22, 31, 31, 29, 31, 37, 30, 32, 36, 32, 35, 34, 37, 36, 39, 39, 41, 38, 39, 51, 47, 48, 35, 42, 48

Offset: 6

Author

Michel Lagneau, Dec 23 2011

Keywords

• nonn
• base
• easy

Comments

(sum of digits of n!) / 9 is an integer for n > 5.

Links

• Seiichi Manyama, Table of n, a(n) for n = 6..10000

Crossrefs

Cf. A004152, A086358.

Programs

Mathematica

Table[Sum[DigitCount[n!][[i]]*i/9, {i, 1, 9}], {n, 6, 100}]
Total[IntegerDigits[#]]/9&/@(Range[6,80]!) (* Harvey P. Dale, Nov 22 2023 *)

PARI

a(n) = sumdigits(n!)/9; \\ Michel Marcus, Aug 12 2022

Formula

a(n) = A004152(n)/9.