A004773 -id:A004773 - cp's OEIS frontend

A369464 Numbers for which there is no representation as a sum (pq + pr + q*r) with three odd primes p <= q <= r.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 88

Offset: 1

Antti Karttunen, Jan 24 2024

nonn

Complement of A369251. Numbers not in A369252.
Union of A004773 and A369056.
Positions of 0's in A369054.
Cf. A098700, A369248, A369249, A369463 (subsequences).

isA369251(n) = if(3!=(n%4),0, my(v = [3,3], ip = #v, r); while(1, r = (n-(v[1]*v[2])) / (v[1]+v[2]); if(r < v[2], ip--, ip = #v; if(1==denominator(r) && isprime(r), return(1))); if(!ip, return(0)); v[ip] = nextprime(1+v[ip]); for(i=1+ip,#v,v[i]=v[i-1])));
isA369464(n) = !isA369251(n);

A189785 a(n) = n+floor(n*r/s)+floor(nt/s); r=Pi/2, s=arcsin(5/13), t=arcsin(12/13).

Original entry on oeis.org

6, 14, 22, 30, 38, 46, 54, 62, 70, 78, 86, 94, 102, 110, 118, 126, 134, 142, 150, 158, 166, 174, 182, 190, 198, 206, 214, 222, 230, 238, 246, 254, 262, 270, 278, 286, 294, 302, 310, 318, 326, 334, 342, 350, 358, 366, 374, 380, 388, 396, 404, 412, 420, 428, 436, 444, 452, 460, 468, 476, 484, 492, 500, 508, 516, 524, 532, 540, 548

Offset: 1

Clark Kimberling, Apr 27 2011

nonn

This is one of three sequences that partition the positive integers.  In general, suppose that r, s, t are positive real numbers for which the sets {i/r: i>=1}, {j/s: j>=1}, {k/t: k>=1} are pairwise disjoint.  Let a(n) be the rank of n/r when all the numbers in the three sets are jointly ranked.  Define b(n) and c(n) as the ranks of n/s and n/t.  It is easy to prove that
a(n)=n+[ns/r]+[nt/r],
b(n)=n+[nr/s]+[nt/s],
c(n)=n+[nr/t]+[ns/t], where []=floor.
Taking r=Pi/2, s=arcsin(5/13), t=arcsin(12/13) gives
a=A005408, b=A189785, c=A189786.  Note that r=s+t.
a(n) first differs from A017137(n-1) at n=48 (a(48)=380 but A017137(47)=382). - Nathaniel Johnston, May 16 2011

Cf. A189786, A189787, A004773.

r=Pi/2; s=ArcSin[5/13]; t=ArcSin[12/13];
a[n_] := n + Floor[n*s/r] + Floor[n*t/r];
b[n_] := n + Floor[n*r/s] + Floor[n*t/s];
c[n_] := n + Floor[n*r/t] + Floor[n*s/t];
Table[a[n], {n, 1, 120}]  (*A005408*)
Table[b[n], {n, 1, 120}]  (*A189785*)
Table[c[n], {n, 1, 120}]  (*A189786*)
Table[b[n]/2, {n, 1, 120}]  (*A189787*)
Table[c[n]/2, {n, 1, 120}]  (*A004773*)

A319949 a(n) = Product_{i=1..n} floor(4*i/3).

Original entry on oeis.org

1, 2, 8, 40, 240, 1920, 17280, 172800, 2073600, 26956800, 377395200, 6038323200, 102651494400, 1847726899200, 36954537984000, 776045297664000, 17072996548608000, 409751917166592000, 10243797929164800000, 266338746158284800000

Offset: 1

Vaclav Kotesovec, Oct 02 2018

nonn

Harvey P. Dale, Table of n, a(n) for n = 1..429

Cf. A004773, A010786, A180736, A275062, A319948, A319950.

Table[Product[Floor[i*4/3], {i, 1, n}], {n, 1, 20}]
RecurrenceTable[{27*(3*n - 7)*a[n] == 54*(2*n - 5)*a[n-1] + 12*(12*n^2 - 42*n + 35)*a[n-2] + 8*(n-2)*(2*n - 5)*(3*n - 4)*(4*n - 9)*a[n-3], a[1]==1, a[2]==2, a[3]==8}, a, {n, 1, 20}]
FoldList[Times,Floor[4 Range[20]/3]] (* Harvey P. Dale, Mar 21 2024 *)

a(n) = prod(i=1, n, (4*i)\3); \\ Michel Marcus, Oct 03 2018

a(n) ~ (4/3)^n * n! * 2*sqrt(Pi) / (3^(1/4) * Gamma(1/4) * n^(1/4)).

Recurrence: 27*(3*n - 7)*a(n) = 54*(2*n - 5)*a(n-1) + 12*(12*n^2 - 42*n + 35)*a(n-2) + 8*(n-2)*(2*n - 5)*(3*n - 4)*(4*n - 9)*a(n-3).

A104401 a(n) = A104235(n)/4.

Original entry on oeis.org

0, 1, 2, 4, 5, 6, 8, 9, 10, 12, 13, 14, 16, 17, 18, 20, 21, 22, 24, 25, 26, 28, 29, 30, 32, 33, 34, 36, 37, 38, 40, 41, 42, 44, 45, 46, 48, 49, 50, 52, 53, 54, 56, 57, 58, 60, 61, 64, 65, 66, 68, 69, 70, 72, 73, 74, 76, 77, 78

Offset: 0

N. J. A. Sloane, Apr 18 2005

nonn

First differs from A004773(n)=floor(4n/3) at a(47)=64 vs A004773(47)=62. - M. F. Hasler, Oct 05 2014

David Applegate, Benoit Cloitre, Philippe Deléham and N. J. A. Sloane, Sloping binary numbers: a new sequence related to the binary numbers [pdf, ps].
David Applegate, Benoit Cloitre, Philippe Deléham and N. J. A. Sloane, Sloping binary numbers: a new sequence related to the binary numbers, J. Integer Seq. 8 (2005), no. 3, Article 05.3.6, 15 pp.

Cf. A004773, A104235

A260113 Maximum number of queens on an n X n chessboard such that no queen attacks more than one other queen.

Original entry on oeis.org

1, 2, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 17, 18, 20, 21, 22, 24, 25, 26, 28, 29, 30, 32, 33, 34, 36, 37, 38, 40

Offset: 1

Rob Pratt, Jul 16 2015

nonn

Can be formulated as an integer linear programming problem as follows. Define a graph with a node for each cell and an edge for each pair of cells that are a queen's move apart. Let binary variable x[i] = 1 if a queen appears at node i, and 0 otherwise. The objective is to maximize sum x[i]. Let N[i] be the set of neighbors of node i. To enforce the rule that x[i] = 1 implies sum {j in N[i]} x[j] <= 1, impose the linear constraint sum {j in N[i]} x[j] - 1 <= (|N[i]| - 1) * (1 - x[i]) for each i.
An alternative formulation uses constraints x[i] + x[j] + x[k] <= 2 for each forbidden triple of nodes.
Taking into account known values, it is reasonable to conjecture that a(n) = floor(4*n/3) for n > 5. - Giovanni Resta, Aug 07 2015.
a(n) = floor(4*n/3) for large n. - Géza Makay, Dec 13 2024

			a(8) = 10:
  X-------
  ----XX--
  -X------
  -X------
  ------X-
  ------X-
  --XX----
  X-------

IBM, Ponder This Challenge, August 2008 (a(30) = 40 and upper bound a(n) <= 4n / 3).
Géza Makay, Proof that a(n) = floor(4*n/3) for large n (in Hungarian).
Giovanni Resta, Illustration of a(6)-a(30)
Manfred Scheucher, Python Script

A260090 is the corresponding sequence for kings.

Cf. A004773 (after Resta).

Ponder This solution page shows a(6n) = 8n.

a(16)-a(30) from Giovanni Resta, Aug 07 2015

A345118 a(n) is the sum of the lengths of all the segments used to draw a square of side n representing a basketweave pattern where all the multiple strands are of unit width, the horizontal ones appearing as 1 X 3 rectangles, while the vertical ones as unit area squares.

Original entry on oeis.org

0, 4, 11, 20, 34, 50, 69, 92, 116, 144, 175, 208, 246, 286, 329, 376, 424, 476, 531, 588, 650, 714, 781, 852, 924, 1000, 1079, 1160, 1246, 1334, 1425, 1520, 1616, 1716, 1819, 1924, 2034, 2146, 2261, 2380, 2500, 2624, 2751, 2880, 3014, 3150, 3289, 3432, 3576, 3724

Offset: 0

Stefano Spezia, Jun 08 2021

			Illustrations for n = 1..8:
        _           _ _          _ _ _
       |_|         |_|_|        |_ _ _|
                   |_ _|        |_|_|_|
                                |_ _ _|
    a(1) = 4     a(2) = 11     a(3) = 20
     _ _ _ _     _ _ _ _ _    _ _ _ _ _ _
    |_ _|_|_|   |_ _|_|_ _|  |_|_|_ _ _|_|
    |_|_ _ _|   |_|_ _ _|_|  |_ _ _|_|_ _|
    |_ _|_|_|   |_ _|_|_ _|  |_|_|_ _ _|_|
    |_|_ _ _|   |_|_ _ _|_|  |_ _ _|_|_ _|
                |_ _|_|_ _|  |_|_|_ _ _|_|
                             |_ _ _|_|_ _|
    a(4) = 34    a(5) = 50     a(6) = 69
      _ _ _ _ _ _ _      _ _ _ _ _ _ _ _
     |_|_|_ _ _|_|_|    |_ _|_|_ _ _|_|_|
     |_ _ _|_|_ _ _|    |_|_ _ _|_|_ _ _|
     |_|_|_ _ _|_|_|    |_ _|_|_ _ _|_|_|
     |_ _ _|_|_ _ _|    |_|_ _ _|_|_ _ _|
     |_|_|_ _ _|_|_|    |_ _|_|_ _ _|_|_|
     |_ _ _|_|_ _ _|    |_|_ _ _|_|_ _ _|
     |_|_|_ _ _|_|_|    |_ _|_|_ _ _|_|_|
                        |_|_ _ _|_|_ _ _|
        a(7) = 92           a(8) = 116

Index entries for linear recurrences with constant coefficients, signature (3,-3,1,-1,3,-3,1).

Cf. A000035, A004773, A056594, A115067, A211014, A316316, A316317, A368052.

LinearRecurrence[{3,-3,1,-1,3,-3,1},{0,4,11,20,34,50,69},50]
a[ n_] := (3*n^2 + 5*n)/2 - (-1)^Floor[n/4]*Boole[Mod[n, 4] == 3]; (* Michael Somos, Jan 25 2024 *)

concat(0, Vec(x*(4 - x - x^2 + 3*x^3 + x^4)/((1 - x)^3*(1 + x^4)) + O(x^40))) \\ Felix Fröhlich, Jun 09 2021

{a(n) = (3*n^2 + 5*n)/2 - (-1)^(n\4)*(n%4==3)}; /* Michael Somos, Jan 25 2024 */

O.g.f.: x*(4 - x - x^2 + 3*x^3 + x^4)/((1 - x)^3*(1 + x^4)).
E.g.f.: (exp(x)*x*(8 + 3*x) + (-1)^(1/4)*(sinh((-1)^(1/4)*x) - sin((-1)^(1/4)*x)))/2.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) - a(n-4) + 3*a(n-5) - 3*a(n-6) + a(n-7) for n > 6.
a(n) = (n*(5 + 3*n) - (1 - (-1)^n)*sin((n-1)*Pi/4))/2.
a(n) = A211014(n/2) - A000035(n)*A056594((n-3)/2).
a(2*n) = A211014(n).
a(k) = A115067(k+1) for k not congruent to 3 mod 4 (A004773).
From Helmut Ruhland, Jan 29 2024: (Start)
For n > 1: a(n) - (2 * A368052(n+2) + A368052(n+3)) * 2 is periodic for n mod 8, i.e. a(n) = (2 * A368052(n+2) + A368052(n+3)) * 2 + f8(n) with
n mod 8 =   0   1   2   3   4   5   6   7
f8(n)   =   0   0  -3  -2  -2  -2   1   0   (End)

A361804 Number of partitions of [n] with an equal number of even and odd block sizes.

Original entry on oeis.org

1, 0, 0, 3, 0, 15, 45, 63, 1260, 1515, 25515, 104973, 510345, 5679765, 17252235, 263214318, 1207222380, 11863296915, 101718989235, 630468648873, 8281982665215, 48583038314415, 656006633919945, 5122900223419938, 54304561161840825, 605082149235374265

Offset: 0

Alois P. Heinz, Jun 12 2023

nonn

Half the number of block sizes are even and the other half are odd.

			a(0) = 1: () the empty partition.
a(1) = 0.
a(2) = 0.
a(3) = 3: 12|3, 13|2, 1|23.
a(4) = 0.
a(5) = 15: 1234|5, 1235|4, 123|45, 1245|3, 124|35, 125|34, 12|345, 1345|2, 134|25, 135|24, 13|245, 145|23, 14|235, 15|234, 1|2345.
a(6) = 45: 12|34|5|6, 12|35|4|6, 12|3|45|6, 12|36|4|5, 12|3|46|5, 12|3|4|56, 13|24|5|6, 13|25|4|6, 13|2|45|6, 13|26|4|5, 13|2|46|5, 13|2|4|56, 14|23|5|6, 15|23|4|6, 1|23|45|6, 16|23|4|5, 1|23|46|5, 1|23|4|56, 14|25|3|6, 14|2|35|6, 14|26|3|5, 14|2|36|5, 14|2|3|56, 15|24|3|6, 1|24|35|6, 16|24|3|5, 1|24|36|5, 1|24|3|56, 15|2|34|6, 1|25|34|6, 16|2|34|5, 1|26|34|5, 1|2|34|56, 15|26|3|4, 15|2|36|4, 15|2|3|46, 16|25|3|4, 1|25|36|4, 1|25|3|46, 16|2|35|4, 1|26|35|4, 1|2|35|46, 16|2|3|45, 1|26|3|45, 1|2|36|45.

Alois P. Heinz, Table of n, a(n) for n = 0..576
Wikipedia, Partition of a set

Cf. A000110, A003724, A004767, A004773, A005046, A275679.

b:= proc(n, x, y) option remember; `if`(abs(x-y)>2*n, 0,
     `if`(n=0, 1, b(n-1, x+1, y)+`if`(x>0, b(n-1, x-1, y+1)*x, 0)+
     `if`(y>0, b(n-1, x+1, y-1)*y, 0)))
    end:
a:= n-> b(n, 0$2):
seq(a(n), n=0..33);

a(n) mod 5 = 3 for n in { A004767 }, a(n) mod 5 = 1 for n = 0 and a(n) mod 5 = 0 for all other n (n in { A004773 } \ { 0 }).

a(n) mod 3 = 0 for n >= 1.

A047400 Numbers that are congruent to {1, 3, 6} mod 8.

Original entry on oeis.org

1, 3, 6, 9, 11, 14, 17, 19, 22, 25, 27, 30, 33, 35, 38, 41, 43, 46, 49, 51, 54, 57, 59, 62, 65, 67, 70, 73, 75, 78, 81, 83, 86, 89, 91, 94, 97, 99, 102, 105, 107, 110, 113, 115, 118, 121, 123, 126, 129, 131, 134, 137, 139, 142, 145, 147, 150, 153, 155, 158

Offset: 1

N. J. A. Sloane

Union of A017077, A017101 and A017137. - R. J. Mathar, Apr 14 2008

Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).

Cf. A004773.

Cf. A017077, A017101, A017137.

[n: n in [1..300] | n mod 8 in [1, 3, 6]]; // Vincenzo Librandi, Mar 27 2011

A047400:=n->2*(12*n-9+sqrt(3)*sin(2*n*Pi/3))/9: seq(A047400(n), n=1..100); # Wesley Ivan Hurt, Jun 10 2016

Select[Range[0, 150], MemberQ[{1, 3, 6}, Mod[#, 8]] &] (* Wesley Ivan Hurt, Jun 10 2016 *)

a(n) = {x=8*floor((n-1)/3);if(n%3==1,x=x+1);if(n%3==2,x=x+3);if(n%3==0,x=x+6);x} \\ Michael B. Porter, Oct 02 2009

a(n) = A004773(n-1) + A004773(n). - Gary W. Adamson, Sep 13 2007
G.f.: x*(1+x)*(2x^2+x+1)/((-1+x)^2*(x^2+x+1)). a(n) = a(n-3)+8 for n>3. - R. J. Mathar, Apr 14 2008
From Wesley Ivan Hurt, Jun 10 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = 2*(12*n-9+sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 8k-2, a(3k-1) = 8k-5, a(3k-2) = 8k-7. (End)

A222170 a(n) = n^2 + 2*floor(n^2/3).

Original entry on oeis.org

0, 1, 6, 15, 26, 41, 60, 81, 106, 135, 166, 201, 240, 281, 326, 375, 426, 481, 540, 601, 666, 735, 806, 881, 960, 1041, 1126, 1215, 1306, 1401, 1500, 1601, 1706, 1815, 1926, 2041, 2160, 2281, 2406, 2535, 2666, 2801, 2940, 3081, 3226, 3375, 3526, 3681, 3840

Offset: 0

Bruno Berselli, Aug 08 2013

Also, a(n) = n^2 + floor(2*n^2/3), since 2*floor(n^2/3) = floor(2*n^2/3).

Bruno Berselli, Table of n, a(n) for n = 0..1000
Tadeusz Dorozinskis, Pentagonpolyhedra Doro
Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).

Subsequence of A008851.

Cf. A004773 (numbers of the type n+floor(n/3)), A008810 (numbers of the type n^2-2*floor(n^2/3)), A047220 (numbers of the type n+floor(2*n/3)), A184637 (numbers of the type n^2+floor(n^2/3), except the first two).

Magma
```
[n^2+2*Floor(n^2/3): n in [0..50]];
```

I:=[0,1,6,15,26]; [n le 5 select I[n] else 2*Self(n-1)-Self(n-2)+Self(n-3)-2*Self(n-4)+Self(n-5): n in [1..50]]; // Vincenzo Librandi, Aug 18 2013

Table[n^2 + 2 Floor[n^2/3], {n, 0, 50}]
CoefficientList[Series[x (1 + x) (1 + 3 x + x^2) / ((1 + x + x^2) (1 - x)^3), {x, 0, 50}], x] (* Vincenzo Librandi, Aug 18 2013 *)
LinearRecurrence[{2, -1, 1, -2, 1}, {0, 1, 6, 15, 26}, 50] (* Hugo Pfoertner, Jan 17 2023 *)

G.f.: x*(1+x)*(1 + 3*x + x^2)/((1 + x + x^2)*(1-x)^3).
a(n) = a(-n) = 2*a(n-1) - a(n-2) + a(n-3) - 2*a(n-4) + a(n-5).
a(n) = floor(5*n^2/3). - Wesley Ivan Hurt, Mar 16 2015
a(n) = a(n-3) + 5*(2n-3) [Tadeusz Dorozinski]. - Eduard Baumann, Jan 18 2023

A047421 Floor(8n/7).

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 40, 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75

Offset: 0

N. J. A. Sloane

Up to the offset identical to A004777, cf formula. - M. F. Hasler, Oct 06 2014

Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,1,-1).

Cf. A032766, A004773, A001068, A047226, A047368, A004777.

Table[Floor[8 n/7], {n, 0, 80}] (* Bruno Berselli, Oct 06 2014 *)
LinearRecurrence[{1,0,0,0,0,0,1,-1},{0,1,2,3,4,5,6,8},70] (* Harvey P. Dale, Mar 06 2016 *)

PARI
```
a(n)=n\7+n \\ M. F. Hasler, Oct 06 2014
```

a(n) = A004777(n+1). - M. F. Hasler, Oct 06 2014
G.f.: x*(1 + x + x^2 + x^3 + x^4 + x^5 + 2*x^6) / (1 - x - x^7 + x^8). [Bruno Berselli, Oct 06 2014]
a(n) = n + floor(n/7) = a(n-1) + a(n-7) - a(n-8). [Bruno Berselli, Oct 06 2014]

More terms from Ray Chandler, Sep 05 2004

Restored to version of early 2008 by M. F. Hasler, Oct 06 2014

cp's OEIS Frontend

A369464 Numbers for which there is no representation as a sum (p*q + p*r + q*r) with three odd primes p <= q <= r.

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A189785 a(n) = n+floor(n*r/s)+floor(nt/s); r=Pi/2, s=arcsin(5/13), t=arcsin(12/13).

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A319949 a(n) = Product_{i=1..n} floor(4*i/3).

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A104401 a(n) = A104235(n)/4.

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A260113 Maximum number of queens on an n X n chessboard such that no queen attacks more than one other queen.

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A345118 a(n) is the sum of the lengths of all the segments used to draw a square of side n representing a basketweave pattern where all the multiple strands are of unit width, the horizontal ones appearing as 1 X 3 rectangles, while the vertical ones as unit area squares.

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A361804 Number of partitions of [n] with an equal number of even and odd block sizes.

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A047400 Numbers that are congruent to {1, 3, 6} mod 8.

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A222170 a(n) = n^2 + 2*floor(n^2/3).

A369464 Numbers for which there is no representation as a sum (pq + pr + q*r) with three odd primes p <= q <= r.