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Number of divisors of 7*n-6 of form 7*k+1.
0

%I #13 Jun 25 2023 09:42:51

%S 1,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,4,2,2,2,2,2,2,2,4,2,2,2,2,2,2,3,4,

%T 2,2,2,2,2,2,2,4,2,2,2,2,2,4,2,4,2,2,2,2,2,2,2,4,2,2,2,2,4,2,2,4,2,2,

%U 2,3,2,2,2,4,2,2,2,4,2,2,2,4,2,2,2,2,2,2,2,4,2,4,4,2,2,2,2,4,2,2

%N Number of divisors of 7*n-6 of form 7*k+1.

%F a(n) = A279061(7*n-6).

%F G.f.: Sum_{k>0} x^k/(1 - x^(7*k-6)).

%t a[n_] := DivisorSum[7*n - 6, 1 &, Mod[#, 7] == 1 &]; Array[a, 100] (* _Amiram Eldar_, Jun 25 2023 *)

%o (PARI) a(n) = sumdiv(7*n-6, d, d%7==1);

%Y Cf. A359212, A359238, A359309.

%Y Cf. A279061.

%K nonn

%O 1,2

%A _Seiichi Manyama_, Jun 24 2023