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A363859
Number of divisors of 7*n-1 of form 7*k+2.
0
1, 0, 1, 1, 1, 0, 2, 0, 1, 1, 1, 0, 3, 0, 1, 1, 1, 0, 2, 0, 1, 2, 2, 0, 2, 0, 1, 1, 1, 0, 3, 0, 2, 1, 1, 0, 2, 0, 2, 2, 1, 0, 3, 0, 1, 1, 1, 0, 3, 0, 1, 1, 2, 0, 3, 1, 1, 2, 1, 0, 2, 0, 2, 1, 1, 0, 3, 0, 1, 1, 2, 0, 4, 0, 1, 2, 1, 0, 3, 0, 1, 1, 2, 0, 3, 0, 2, 1, 1, 1, 2, 0, 2, 2, 1, 0, 2, 0, 1, 1
OFFSET
1,7
COMMENTS
Also number of divisors of 7*n-1 of form 7*k+3.
FORMULA
a(n) = A363795(7*n-1) = A363805(7*n-1).
G.f.: Sum_{k>0} x^(3*k-2)/(1 - x^(7*k-5)).
G.f.: Sum_{k>0} x^(2*k-1)/(1 - x^(7*k-4)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 1, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-1, d, d%7==2);
CROSSREFS
Sequence in context: A034178 A317531 A074169 * A328458 A099362 A321378
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 24 2023
STATUS
approved