A367466 Sum of the final digits of the divisors of n.

1, 3, 4, 7, 6, 12, 8, 15, 13, 8, 2, 18, 4, 14, 14, 21, 8, 29, 10, 12, 12, 6, 4, 30, 11, 12, 20, 26, 10, 22, 2, 23, 8, 14, 18, 41, 8, 20, 16, 20, 2, 26, 4, 14, 28, 12, 8, 44, 17, 13, 12, 18, 4, 40, 12, 40, 20, 20, 10, 28, 2, 6, 24, 27, 14, 24, 8, 26, 16, 24, 2, 55, 4

Offset: 1

Author

Wesley Ivan Hurt, Nov 18 2023

Keywords

• nonn
• base
• easy

Comments

First differs from A093811 at a(21) = 12.

Inverse Möbius transform of (n mod 10) (A010879). - Wesley Ivan Hurt, Jun 23 2024

Examples

			a(21) = 12; The divisors of 21 are {1, 3, 7, 21} and the sum of the final digits of the divisors is 1 + 3 + 7 + 1 = 12.
		

Crossrefs

Cf. A010879, A093811.

Programs

Maple

f:= proc(n) add(t mod 10, t = numtheory:-divisors(n)) end proc:
map(f, [$1..100]); # Robert Israel, Nov 19 2023

Mathematica

Table[DivisorSum[n, Mod[#, 10] &], {n, 100}]

PARI

a(n) = sumdiv(n, d, d%10); \\ Michel Marcus, Nov 19 2023

Formula

a(n) = Sum_{d|n} (d mod 10).