A293896 -id:A293896 - cp's OEIS frontend

A319992 a(n) = Product_{d|n, dA019565(d)^[2 == d mod 3].

1, 1, 1, 3, 1, 3, 1, 3, 1, 30, 1, 3, 1, 3, 10, 21, 1, 3, 1, 30, 1, 126, 1, 21, 10, 3, 1, 315, 1, 30, 1, 21, 42, 66, 10, 3, 1, 3, 1, 11550, 1, 315, 1, 126, 10, 990, 1, 21, 1, 30, 22, 693, 1, 3, 420, 2205, 1, 2310, 1, 1650, 1, 3, 1, 273, 10, 126, 1, 66, 330, 245700, 1, 21, 1, 3, 10, 585, 42, 693, 1, 11550, 1, 546, 1, 315, 220, 3, 770

Offset: 1

Antti Karttunen, Oct 03 2018

nonn

Antti Karttunen, Table of n, a(n) for n = 1..8192

Cf. A019565, A293214, A293896, A293898, A319990, A319991, A320005, A320012 (rgs-transform).

Cf. also A293222.

A019565(n) = {my(j,v); factorback(Mat(vector(if(n, #n=vecextract(binary(n), "-1..1")), j, [prime(j), n[j]])~))}; \\ From A019565
A319992(n) = { my(m=1); fordiv(n,d,if((dA019565(d))); m; };

a(n) = Product_{d|n, dA019565(d)^[2 == d mod 3].
a(n) = A293214(n) / (A319990(n)*A319991(n)).
For all n >= 1:
A007814(a(n)) = A320005(n).
A048675(a(n)) = A293898(n).
A195017(a(n)) = -A293896(n) mod 3.

A293895 Number of proper divisors of n of the form 3k+1.

Original entry on oeis.org

0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 3, 2, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 1, 2, 2, 1, 2, 2, 3, 1, 2, 1, 3, 1, 1, 1, 3, 2, 3, 1, 3, 1, 1, 1, 4, 2, 1, 1, 3, 1, 2, 2, 3, 2, 2, 1, 3, 1, 3, 1, 2, 1, 2, 2, 3, 2, 2, 1, 5, 1, 1, 1, 4, 1, 2, 1, 3, 1, 2, 3, 3, 2, 1, 2, 3, 1, 3, 1, 4, 1, 2, 1, 4, 2

Offset: 1

Antti Karttunen, Nov 06 2017

Antti Karttunen, Table of n, a(n) for n = 1..20000
R. A. Smith and M. V. Subbarao, The average number of divisors in an arithmetic progression, Canadian Mathematical Bulletin, Vol. 24, No. 1 (1981), pp. 37-41.

Cf. A001620, A001817, A256425, A293451, A293896, A293897, A293899.

Table[DivisorSum[n, 1 &, And[Mod[#, 3] == 1, # != n] &], {n, 105}] (* Michael De Vlieger, Nov 08 2017 *)

PARI
```
A293895(n) = sumdiv(n,d,(d
				
```

a(n) = A001817(n) - [n == 1 (mod 3)].
G.f.: Sum_{k>=1} x^(6*k-4) / (1 - x^(3*k-2)). - Ilya Gutkovskiy, Apr 14 2021
Sum_{k=1..n} a(k) = n*log(n)/3 + c*n + O(n^(1/3)*log(n)), where c = gamma(1,3) - (2 - gamma)/3 = A256425 - (2 - A001620)/3 = 0.203545... (Smith and Subbarao, 1981). - Amiram Eldar, Nov 25 2023

A320005 Number of proper divisors of n of the form 6*k + 5.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 2, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 2, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 2, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 2

Offset: 1

Antti Karttunen, Oct 03 2018

Antti Karttunen, Table of n, a(n) for n = 1..65537
R. A. Smith and M. V. Subbarao, The average number of divisors in an arithmetic progression, Canadian Mathematical Bulletin, Vol. 24, No. 1 (1981), pp. 37-41.

Cf. A293896, A319992, A319995, A320001, A320003, A320015.

Cf. A001620, A016629, A222458 (psi(5/6)).

a[n_] := DivisorSum[n, 1 &, # < n && Mod[#, 6] == 5 &]; Array[a, 100] (* Amiram Eldar, Nov 25 2023 *)

A320005(n) = if(!n,n,sumdiv(n, d, (d

a(n) = A319995(n) - [+5 = n (mod 6)], where [ ] is the Iverson bracket, giving 1 only when n = -1 mod 6, and 0 otherwise.
a(n) = A320015(n) - A320001(n).
a(n) = A007814(A319992(n)).
G.f.: Sum_{k>=1} x^(12*k-2) / (1 - x^(6*k-1)). - Ilya Gutkovskiy, Apr 14 2021
Sum_{k=1..n} a(k) = n*log(n)/6 + c*n + O(n^(1/3)*log(n)), where c = gamma(5,6) - (2 - gamma)/6 = -0.387302..., gamma(5,6) = -(psi(5/6) + log(6))/6 is a generalized Euler constant, and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Nov 25 2023

A293898 Sum of proper divisors of n of the form 3k+2.

Original entry on oeis.org

0, 0, 0, 2, 0, 2, 0, 2, 0, 7, 0, 2, 0, 2, 5, 10, 0, 2, 0, 7, 0, 13, 0, 10, 5, 2, 0, 16, 0, 7, 0, 10, 11, 19, 5, 2, 0, 2, 0, 35, 0, 16, 0, 13, 5, 25, 0, 10, 0, 7, 17, 28, 0, 2, 16, 24, 0, 31, 0, 27, 0, 2, 0, 42, 5, 13, 0, 19, 23, 56, 0, 10, 0, 2, 5, 40, 11, 28, 0, 35, 0, 43, 0, 16, 22, 2, 29, 65, 0, 7, 0, 25, 0, 49, 5, 42, 0, 16, 11, 77, 0, 19, 0, 36, 40

Offset: 1

Antti Karttunen, Nov 06 2017

Antti Karttunen, Table of n, a(n) for n = 1..20000
Index entries for sequences related to sums of divisors.

Cf. A078182, A293896, A293897.

Table[DivisorSum[n, # &, And[Mod[#, 3] == 2, # != n] &], {n, 105}] (* Michael De Vlieger, Nov 08 2017 *)

PARI
```
A293898(n) = sumdiv(n,d,(d
				
```

a(n) = A078182(n) - ([n == 2 (mod 3)]*n).
G.f.: Sum_{k>=1} (3*k-1) * x^(6*k-2) / (1 - x^(3*k-1)). - Ilya Gutkovskiy, Apr 14 2021
Sum_{k=1..n} a(k) = c * n^2 + O(n*log(n)), where c = Pi^2/36  - 1/6 = 0.107489... . - Amiram Eldar, Nov 27 2023

A320015 Number of proper divisors of n that are either of the form 6k+1 or 6k + 5.

Original entry on oeis.org

0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 2, 1, 1, 2, 2, 3, 1, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 1, 2, 3, 2, 2, 1, 1, 3, 2, 2, 2, 1, 2, 1, 2, 2, 1, 3, 2, 1, 2, 2, 4, 1, 1, 1, 2, 3, 2, 3, 2, 1, 2, 1, 2, 1, 2, 3, 2, 2, 2, 1, 2, 3, 2, 2, 2, 3, 1, 1, 3, 2, 3, 1, 2, 1, 2, 4

Offset: 1

Antti Karttunen, Oct 03 2018

Antti Karttunen, Table of n, a(n) for n = 1..65537
R. A. Smith and M. V. Subbarao, The average number of divisors in an arithmetic progression, Canadian Mathematical Bulletin, Vol. 24, No. 1 (1981), pp. 37-41.

Cf. A001620, A035218, A232991, A293895, A293896, A320001, A320005.

a[n_] := DivisorSum[n, 1 &, # < n && MemberQ[{1, 5}, Mod[#, 6]] &]; Array[a, 100] (* Amiram Eldar, Nov 25 2023 *)

A320015(n) = if(!n,n,sumdiv(n, d, (d

a(n) = A320001(n) + A320005(n).
a(n) = A035218(n) - ch15(n), where ch15 is the characteristic function of numbers of the form +-1 mod 6, i.e., ch15(n) = A232991(n-1).
Sum_{k=1..n} a(k) = n*log(n)/3 + c*n + O(n^(1/3)*log(n)), where c = 2*(gamma + log(12)/4 - 1)/3 = 0.132294..., and gamma is Euler's constant (A001620) (Smith and Subbarao, 1981). - Amiram Eldar, Nov 25 2023

A293899 Number of proper divisors of the form 3k+1 minus number of proper divisors of the form 3k+2.

Original entry on oeis.org

0, 1, 1, 0, 1, 0, 1, 1, 1, -1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 2, -1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, -1, 1, 1, 1, 1, 2, -1, 1, 0, 1, 1, 0, -1, 1, 1, 2, 1, 0, 1, 1, 0, -1, 1, 2, -1, 1, 0, 1, 1, 2, 0, 1, 0, 1, 1, 0, -1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, -1, 1, 2, -1, 1, 0, -1, 1, 0, 3, 1, 2, -1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0

Offset: 1

Antti Karttunen, Nov 06 2017

Antti Karttunen, Table of n, a(n) for n = 1..20000

Cf. A002324, A010872, A073010, A293895, A293896.

Table[DivisorSum[n, 1 &, And[Mod[#, 3] == 1, # != n] &] - DivisorSum[n, 1 &, And[Mod[#, 3] == 2, # != n] &], {n, 105}] (* Michael De Vlieger, Nov 08 2017 *)
Table[Total[Which[Mod[#,3]==1,1,Mod[#,3]==2,-1,True,0]&/@Most[ Divisors[ n]]],{n,110}] (* Harvey P. Dale, Nov 26 2021 *)

A293895(n) = sumdiv(n,d,(dA293896(n) = sumdiv(n,d,(dA293899(n) = (A293895(n) - A293896(n));

When n = 3k, a(n) = A002324(n), when n = 3k+1, a(n) = A002324(n) - 1, when n = 3k+2, a(n) = A002324(n) + 1.
a(n) = A002324(n) - A010872(n) (mod 3).
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Pi/(3*sqrt(3)) = 0.604599... (A073010). - Amiram Eldar, Nov 25 2023

cp's OEIS Frontend

A319992 a(n) = Product_{d|n, dA019565(d)^[2 == d mod 3].

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A293895 Number of proper divisors of n of the form 3k+1.

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A320005 Number of proper divisors of n of the form 6*k + 5.

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A293898 Sum of proper divisors of n of the form 3k+2.

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A320015 Number of proper divisors of n that are either of the form 6*k+1 or 6*k + 5.

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Author

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Crossrefs

Programs

Mathematica

PARI

Formula

A293899 Number of proper divisors of the form 3k+1 minus number of proper divisors of the form 3k+2.

Views

Author

Keywords

Links

Crossrefs

Programs

Mathematica

PARI

Formula

A320015 Number of proper divisors of n that are either of the form 6k+1 or 6k + 5.