A284151 Sum_{d|n, d=1 or 6 mod 7} d.

1, 1, 1, 1, 1, 7, 1, 9, 1, 1, 1, 7, 14, 1, 16, 9, 1, 7, 1, 21, 1, 23, 1, 15, 1, 14, 28, 1, 30, 22, 1, 9, 1, 35, 1, 43, 1, 1, 14, 29, 42, 7, 44, 23, 16, 1, 1, 63, 1, 51, 1, 14, 1, 34, 56, 9, 58, 30, 1, 42, 1, 63, 1, 73, 14, 29, 1, 35, 70, 1, 72, 51, 1, 1, 16, 77, 1

Offset: 1

Author

Seiichi Manyama, Mar 21 2017

Keywords

• nonn

Links

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

Crossrefs

Cf. A035430, A284099, A284105.

Cf. Sum_{d|n, d=1 or k-1 mod k} d: A046913 (k=3), A000593 (k=4), A284150 (k=5), A186099 (k=6), this sequence (k=7).

Programs

Mathematica

Table[Sum[If[Mod[d, 7] == 1 || Mod[d, 7]==6, d, 0], {d, Divisors[n]}], {n, 80}] (* Indranil Ghosh, Mar 21 2017 *)

PARI

for(n=1, 80, print1(sumdiv(n, d, if(d%7==1 || d%7==6, d, 0)), ", ")) \\ Indranil Ghosh, Mar 21 2017

Python

from sympy import divisors
def a(n): return sum([d for d in divisors(n) if d%7==1 or d%7 == 6]) # Indranil Ghosh, Mar 21 2017

Formula

a(n) = A284099(n) + A284105(n). - R. J. Mathar, Mar 21 2017