A284344 Sum of the divisors of n that are not divisible by 10.

1, 3, 4, 7, 6, 12, 8, 15, 13, 8, 12, 28, 14, 24, 24, 31, 18, 39, 20, 12, 32, 36, 24, 60, 31, 42, 40, 56, 30, 32, 32, 63, 48, 54, 48, 91, 38, 60, 56, 20, 42, 96, 44, 84, 78, 72, 48, 124, 57, 33, 72, 98, 54, 120, 72, 120, 80, 90, 60, 48, 62, 96, 104, 127, 84, 144

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Formula

G.f.: Sum_{k>=1} k*x^k/(1 - x^k) - 10*k*x^(10*k)/(1 - x^(10*k)). - Ilya Gutkovskiy, Mar 25 2017

Sum_{k=1..n} a(k) ~ (3*Pi^2/40) * n^2. - Amiram Eldar, Oct 04 2022

Mathematica

Table[Sum[Boole[Mod[d, 10]>0] d , {d, Divisors[n]}], {n, 100}] (* Indranil Ghosh, Mar 25 2017 *)
Table[Total[Select[Divisors[n], Last[IntegerDigits[#]]!=0&]], {n, 70}] (* Harvey P. Dale, Jun 29 2022 *)

Prog

(PARI) for(n=1, 100, print1(sumdiv(n, d, ((d%10)>0)*d), ", ")) \\ Indranil Ghosh, Mar 25 2017
(Python)
from sympy import divisors
print([sum([i for i in divisors(n) if i%10]) for n in range(1, 101)]) # Indranil Ghosh, Mar 25 2017

Crossrefs

Cf. A261776.

Cf. Sum of the divisors of n that are not divisible by k: A046913 (k=3), A046897 (k=4), A116073 (k=5), A284326 (k=6), A113957 (k=7), A284341 (k=8), A116607 (k=9), this sequence (k=10).

Sequence in context: A367466 A093811 A088000 * A168338 A034690 A069192

Adjacent sequences: A284341 A284342 A284343 * A284345 A284346 A284347

Keyword

nonn

Author

Seiichi Manyama, Mar 25 2017

Status

approved