cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Previous Showing 21-30 of 33 results. Next

A093392 [n/25] + [(n+1)/25] + [(n+2)/25] + [(n+3)/25] + [(n+4)/25].

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 7, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 12, 13, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15
Offset: 0

Views

Author

Reinhard Zumkeller, Mar 28 2004

Keywords

Comments

Conjectured g.f. confirmed with more terms similar to A093390, A093391, A093393.

Crossrefs

Programs

  • Mathematica
    Table[Total[Table[Floor[(n+d)/25],{d,0,4}]],{n,0,90}] (* Harvey P. Dale, Sep 04 2024 *)

Formula

Empirical g.f.: x^21 / ((x-1)^2*(x^20+x^15+x^10+x^5+1)). - Colin Barker, Apr 01 2013

A093393 [n/9] + [n/4] + [(n+1)/9] + [(n+1)/4] + [(n+2)/9].

Original entry on oeis.org

0, 0, 0, 1, 2, 2, 2, 4, 6, 7, 7, 8, 9, 9, 9, 10, 12, 13, 14, 15, 16, 16, 16, 17, 18, 19, 20, 22, 23, 23, 23, 24, 25, 25, 26, 28, 30, 30, 30, 31, 32, 32, 32, 34, 36, 37, 37, 38, 39, 39, 39, 40, 42, 43, 44, 45, 46, 46, 46, 47, 48, 49, 50, 52, 53, 53, 53, 54, 55, 55, 56, 58, 60, 60
Offset: 0

Views

Author

Reinhard Zumkeller, Mar 28 2004

Keywords

Comments

a(n) = A004524(n) + A093390(n).

Programs

  • Mathematica
    Table[Total[Floor[(n+{0,1,2})/9]]+Total[Floor[(n+{0,1})/4]],{n,0,80}] (* or *) LinearRecurrence[{2,-2,1,1,-2,1,1,-2,2,-1},{0,0,0,1,2,2,2,4,6,7},80] (* Harvey P. Dale, Dec 01 2024 *)

Formula

G.f.:(x^3*(2*x^6+x^4+x^3+1))/((x^2+1)*(x^6+x^3+1)*(x-1)^2) [From Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009]

A092038 a(n+1) = a(n) + (a(n) mod 2)^(n mod a(n)), a(1) = 1.

Original entry on oeis.org

1, 2, 2, 3, 4, 4, 4, 5, 6, 6, 6, 7, 8, 8, 8, 9, 10, 10, 10, 11, 12, 12, 12, 13, 14, 14, 14, 15, 16, 16, 16, 17, 18, 18, 18, 19, 20, 20, 20, 21, 22, 22, 22, 23, 24, 24, 24, 25, 26, 26, 26, 27, 28, 28, 28, 29, 30, 30, 30, 31, 32, 32, 32, 33, 34, 34, 34, 35, 36, 36, 36, 37, 38, 38
Offset: 1

Views

Author

Reinhard Zumkeller, Mar 27 2004

Keywords

Comments

a(n) = floor(n/4) + floor((n-1)/4) + 2 for n>1.

Crossrefs

Cf. A004524.

Programs

  • Haskell
    a092038 n = a092038_list !! (n-1)
    a092038_list = 1 : zipWith (\u v -> v + (v `mod` 2) ^ (u `mod` v))
                               [2..] a092038_list
    -- Reinhard Zumkeller, Oct 10 2012
  • Mathematica
    Join[{1},Table[Floor[n/4]+Floor[(n-1)/4]+2,{n,2,80}]] (* Harvey P. Dale, Oct 03 2012 *)

A158856 Triangle T(n, k) = coefficients of p(n, x), where p(n, x) = (1 - x^(2+floor((n-1)/2)))*(1 + (-1)^floor(n/2)*x^(1+floor(n/2))), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 0, -1, 1, 0, 0, -1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, -1, 0, -1, 1, 0, 1, 0, 0, -1, 0, -1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, -1, 0, -1, 0, -1
Offset: 0

Views

Author

Roger L. Bagula, Mar 28 2009

Keywords

Examples

			Triangle begins as:
  1;
  1,  1;
  1,  0, -1;
  1,  0,  0, -1;
  1,  0,  1,  0,  1;
  1,  0,  1,  1,  0,  1;
  1,  0,  1,  0, -1,  0, -1;
  1,  0,  1,  0,  0, -1,  0, -1;
  1,  0,  1,  0,  1,  0,  1,  0,  1;
  1,  0,  1,  0,  1,  1,  0,  1,  0,  1;
  1,  0,  1,  0,  1,  0, -1,  0, -1,  0, -1;
		

Crossrefs

Programs

  • Mathematica
    p[x_, n_]= (1-x^(2+Floor[(n-1)/2]))*(1+(-1)^Floor[n/2]*x^(1+Floor[n/2]))/(1 - x^2);
    Table[CoefficientList[p[x, n], x], {n,0,12}]//Flatten (* modified by G. C. Greubel, Mar 07 2022 *)
  • Sage
    def p(n,x): return (1-x^(2+((n-1)//2)))*(1+(-1)^(n//2)*x^(1+(n//2)))/(1-x^2)
    def A158856(n,k): return ( p(n,x) ).series(x, n+1).list()[k]
    flatten([[A158856(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Mar 07 2022

Formula

T(n, k) = coefficients of p(n, x), where p(n, x) = (Sum_{j=0..1+floor((n-1)/2)} x^j)*(Sum_{i=0..floor(n/2)} (-x)^i) and p(0, x) = 1.
From G. C. Greubel, Mar 07 2022: (Start)
T(n, k) = coefficients of p(n, x), where p(n, x) = (1 - x^(2+floor((n-1)/2)))*(1 + (-1)^floor(n/2)*x^(1+floor(n/2))).
Sum_{k=0..n} T(n, k) = floor((n+3)/2)*( (1 + floor(n/2)) mod 2 ).
Sum_{k=0..n} abs(T(n, k)) = A004524(n+3).
T(2*n, n) = (1 + (-1)^n)/2.
T(2*n+1, n) = (1 + (-1)^n)/2.
Sum_{k=0..floor(n/2)} T(n, k) = floor((n+4)/4).
T(n, k) = abs(A154957(n,k)). (End)

Extensions

Edited by G. C. Greubel, Mar 07 2022

A160636 Hankel transform of A114464.

Original entry on oeis.org

1, 0, -1, -2, -8, 0, 128, 1024, 16384, 0, -4194304, -134217728, -8589934592, 0, 35184372088832, 4503599627370496, 1152921504606846976, 0, -75557863725914323419136, -38685626227668133590597632
Offset: 0

Views

Author

Paul Barry, May 21 2009

Keywords

Comments

Hankel transform of A114464(n+1) is A160637.

Crossrefs

Programs

  • Magma
    R:= RealField(); [Round(2^Floor(Binomial(n,2)/2)*((Sqrt(2)/2 -1/2)*Sin(3*Pi(R)*n/4+Pi(R)/4)+(Sqrt(2)/2+1/2)*Cos(Pi(R)*n/4+Pi(R)/4))): n in [0..50]]; // G. C. Greubel, May 03 2018
    
  • Mathematica
    Table[Round[2^Floor[Binomial[n, 2]/2]*((Sqrt[2]-1)*Sin[(3*n+1)*Pi/4]/2 + (Sqrt[2]+1)*Cos[(n+1)*Pi/4]/2)], {n, 0, 50}] (* G. C. Greubel, May 03 2018 *)
    a[ n_] := -Sign[Mod[n - 1, 4]]*(-1)^Quotient[n - 1, 4]*2^Quotient[n (n - 1), 4]; (* Michael Somos, Mar 14 2020 *)
  • PARI
    for(n=0,50, print1(round(2^floor(binomial(n,2)/2)*((sqrt(2)-1)*sin((3*n+1)*Pi/4)/2 +(sqrt(2)+1)*cos((n+1)*Pi/4)/2)), ", ")) \\ G. C. Greubel, May 03 2018
    
  • PARI
    A160636(n)=if(n%4!=1,(-1)^((n+2)\4)<<(binomial(n,2)\2),0) \\ M. F. Hasler, May 09 2018

Formula

a(n) = 2^floor(C(n,2)/2)*((sqrt(2)-1)*sin((3*n+1)*Pi/4)/2 +(sqrt(2)+1)*cos((n+1)*Pi/4)/2).
a(4k+1) = 0, a(n) = (-1)^floor((n+2)/4) * 2^A011848(n) if n !== 1 (mod 4), where A011848(n) = floor(C(n,2)/2). - M. F. Hasler, May 09 2018
a(n) = -a(2-n) * 2^A004524(n) for all n in Z. - Michael Somos, Mar 14 2020

Extensions

Comment with an incorrect formula deleted by M. F. Hasler, May 09 2018

A166556 Triangle read by rows, A000012 * A047999.

Original entry on oeis.org

1, 2, 1, 3, 1, 1, 4, 2, 2, 1, 5, 2, 2, 1, 1, 6, 3, 2, 1, 2, 1, 7, 3, 3, 1, 3, 1, 1, 8, 4, 4, 2, 4, 2, 2, 1, 9, 4, 4, 2, 4, 2, 2, 1, 1, 10, 5, 4, 2, 4, 2, 2, 1, 2, 1, 11, 5, 5, 2, 4, 2, 2, 1, 3, 1, 1, 12, 6, 6, 3, 4, 2, 2, 1, 4, 2, 2, 1
Offset: 0

Views

Author

Gary W. Adamson, Oct 17 2009

Keywords

Examples

			First few rows of the triangle =
   1;
   2, 1;
   3, 1, 1;
   4, 2, 2, 1;
   5, 2, 2, 1, 1;
   6, 3, 2, 1, 2, 1;
   7, 3, 3, 1, 3, 1, 1;
   8, 4, 4, 2, 4, 2, 2, 1;
   9, 4, 4, 2, 4, 2, 2, 1, 1;
  10, 5, 4, 2, 4, 2, 2, 1, 2, 1;
  11, 5, 5, 2, 4, 2, 2, 1, 3, 1, 1;
  12, 6, 6, 3, 4, 2, 2, 1, 4, 2, 2, 1;
  13, 6, 6, 3, 5, 2, 2, 1, 5, 2, 2, 1, 1;
  ...
		

Crossrefs

Sums include: A006046 (row), A007729 (diagonal).

Programs

  • Magma
    A166556:= func< n,k | (&+[(Binomial(j,k) mod 2): j in [k..n]]) >;
    [A166556(n,k): k in [0..n], n in [0..15]]; // G. C. Greubel, Dec 02 2024
    
  • Maple
    A166556 := proc(n,k)
        local j;
        add(A047999(j,k),j=k..n) ;
    end proc: # R. J. Mathar, Jul 21 2016
  • Mathematica
    A166556[n_, k_]:= Sum[Mod[Binomial[j,k], 2], {j,k,n}];
    Table[A166556[n,k], {n,0,15}, {k,0,n}]//Flatten (* G. C. Greubel, Dec 02 2024 *)
  • Python
    def A166556(n,k): return sum(binomial(j,k)%2 for j in range(k,n+1))
    print(flatten([[A166556(n,k) for k in range(n+1)] for n in range(13)])) # G. C. Greubel, Dec 02 2024

Formula

Triangle read by rows, A000012 * A047999; where A000012 = an infinite lower triangular matrix with all 1's: [1; 1,1; 1,1,1;..]; and A047999 = Sierpinski's gasket.
The operation takes partial sums of Sierpinski's gasket terms, by columns.
From G. C. Greubel, Dec 02 2024: (Start)
T(n, k) = Sum_{j=k..n} (binomial(j,k) mod 2).
T(n, 0) = A000027(n+1).
T(n, 1) = A004526(n+1).
T(n, 2) = A004524(n+1).
T(2*n, n) = A080100(n).
Sum_{k=0..n} T(n, k) = A006046(n+1).
Sum_{k=0..n} (-1)^k*T(n, k) = A006046(floor(n/2)+1).
Sum_{k=0..floor(n/2)} T(n-k, k) = A007729(n). (End)

A187480 Rank transform of the sequence round(n/2); complement of A187481.

Original entry on oeis.org

1, 2, 4, 5, 6, 8, 9, 10, 11, 13, 15, 16, 17, 19, 20, 21, 22, 24, 26, 27, 28, 30, 32, 33, 34, 35, 37, 38, 39, 40, 42, 43, 44, 46, 48, 49, 50, 51, 53, 54, 55, 57, 59, 60, 61, 63, 64, 65, 66, 68, 69, 70, 71, 73, 75, 76, 77, 79, 80, 81, 82, 84, 85, 86, 87, 89, 91, 92, 93, 95, 97, 98, 99, 100, 102, 103, 104, 106, 108, 109, 110, 112, 113, 114, 115, 117, 119, 120, 121, 123, 124, 125
Offset: 1

Views

Author

Clark Kimberling, Mar 10 2011

Keywords

Comments

See A187224. A187480 is the rank transform of (A004525 with initial two zeros removed).

Crossrefs

Programs

  • Mathematica
    seqA = Table[Round[n/2], {n, 1, 180}]  (* A004524 *)
    seqB = Table[n, {n, 1, 80}];           (* A000027 *)
    jointRank[{seqA_, seqB_}] := {Flatten@Position[#1, {_, 1}],
    Flatten@Position[#1, {_, 2}]} &[Sort@Flatten[{{#1, 1} & /@ seqA,
    {#1, 2} & /@ seqB}, 1]];
    limseqU = FixedPoint[jointRank[{seqA, #1[[1]]}] &, jointRank[{seqA, seqB}]][[1]]                                     (* A187480 *)
    Complement[Range[Length[seqA]], limseqU]  (* A187481 *)
    (* by Peter J. C. Moses, Mar 10 2011 *)

A209634 Triangle with (1,4,7,10,13,16...,(3*n-2),...) in every column, shifted down twice.

Original entry on oeis.org

1, 4, 7, 1, 10, 4, 13, 7, 1, 16, 10, 4, 19, 13, 7, 1, 22, 16, 10, 4, 25, 19, 13, 7, 1, 28, 22, 16, 10, 4, 31, 25, 19, 13, 7, 1, 34, 28, 22, 16, 10, 4, 37, 31, 25, 19, 13, 7, 1, 40, 34, 28, 22, 16, 10, 4, 43, 37, 31, 25, 19, 13, 7, 1, 46, 40, 34, 28, 22, 16, 10
Offset: 1

Views

Author

Ctibor O. Zizka, Mar 11 2012

Keywords

Comments

OEIS contains a lot of similar sequences, for example A152204, A122196, A173284.
Row sums for this sequence gives A006578.
In general, by given triangle with (A-B,2*A-B,...,A*n-B,...) in every column, shifted down K-times, we have the row sum s(n)= A*(n*n+K*n+nmodK)/(2*K) - B*(n+nmodK)/K. In this sequence K=2,A=3,B=2, in A152204 K=2,A=2,B=1.
No triangle with primes in every column, shifted down by K>=2 in OEIS, no row sums of it in OEIS.
From Johannes W. Meijer, Sep 28 2013: (Start)
Triangle read by rows formed from antidiagonals of triangle A143971.
The alternating row sums equal A004524(n+2) + 2*A004524(n+1).
The antidiagonal sums equal A171452(n+1). (End)

Examples

			Triangle:
1
4
7,  1
10, 4
13, 7,  1
16, 10, 4
19, 13, 7,  1
22, 16, 10, 4
25, 19, 13, 7,  1
28, 22, 16, 10, 4
...
		

Crossrefs

Programs

  • Maple
    T := (n, k) -> 3*n - 6*k + 4: seq(seq(T(n, k), k=1..floor((n+1)/2)), n=1..15); # Johannes W. Meijer, Sep 28 2013

Formula

From Johannes W. Meijer, Sep 28 2013: (Start)
T(n, k) = 3*n - 6*k + 4, n >= 1 and 1 <= k <= floor((n+1)/2).
T(n, k) = A143971(n-k+1, k), n >= 1 and 1 <= k <= floor((n+1)/2). (End)

A260056 Irregular triangle read by rows: coefficients T(n, k) of certain polynomials p(n, x) with exponents in increasing order, n >= 0 and 0 <= k <= 2*n.

Original entry on oeis.org

1, 2, 1, 1, 3, 3, 4, 2, 1, 4, 6, 10, 9, 7, 3, 1, 5, 10, 20, 25, 26, 19, 11, 4, 1, 6, 15, 35, 55, 71, 70, 56, 34, 16, 5, 1, 7, 21, 56, 105, 161, 196, 197, 160, 106, 55, 22, 6, 1, 8, 28, 84, 182, 322, 462, 554, 553, 463, 321, 183, 83, 29, 7, 1, 9, 36, 120, 294, 588, 966, 1338, 1569, 1570, 1337, 967, 587, 295, 119, 37, 8, 1, 10, 45, 165, 450, 1002, 1848, 2892, 3873, 4477, 4476, 3874
Offset: 0

Views

Author

Werner Schulte, Nov 08 2015

Keywords

Comments

The triangle is related to the triangle of trinomial coefficients.

Examples

			The irregular triangle T(n,k) begins:
n\k:  0   1   2    3    4    5    6    7    8    9   10  11  12  13  14  ...
0     1;
1     2   1   1;
2     3   3   4    2    1;
3     4   6  10    9    7    3    1;
4     5  10  20   25   26   19   11    4    1;
5     6  15  35   55   71   70   56   34   16    5    1;
6     7  21  56  105  161  196  197  160  106   55   22   6   1;
7     8  28  84  182  322  462  554  553  463  321  183  83  29   7   1;
etc.
The polynomial corresponding to row 2 is p(2,x) = 3+3*x+4*x^2+2*x^3+x^4.
		

Crossrefs

Cf. A000027 (col 0), A000217 (col 1), A000292 (col 2), A001590, A002426, A004524, A005582 (col 3), A008937, A027907, A095662 (col 5), A113682, A246437.

Programs

  • Mathematica
    A027907[n_, k_] := Sum[Binomial[n, j]*Binomial[j, k - j], {j, 0, n}]; Table[ Sum[A027907[j, k], {j, 0, n}], {n,0,10}, {k, 0, 2*n} ] // Flatten (* G. C. Greubel, Mar 07 2017 *)

Formula

T(n,0) = n+1, and T(n,k) = 0 for k < 0 or k > 2*n, and T(n+1,k) = T(n,k) + T(n,k-1) + T(n,k-2) for k > 0.
T(n,k) = Sum_{j=0..n} A027907(j,k) for 0 <= k <= 2*n.
T(n,k) = Sum_{j=0..k} (-1)^(k-j)*A027907(n+1,j+1) for 0 <= k <= 2*n.
T(n,k) = T(n,2*n-1-k) + (-1)^k for 0 <= k < 2*n.
p(n,x) = Sum_{k=0..2*n} T(n,k)*x^k = Sum_{k=0..n} (1+x+x^2)^k for n >= 0.
p(n,x) = ((1+x+x^2)^(n+1)-1)/(x+x^2), p(n,0) = p(n,-1) = n+1 for n >= 0.
p(n+1,x) = (1+x+x^2)*p(n,x)+1 for n >= 0.
Sum_{n>=0} p(n,x)*t^n = 1/((1-t)*(1-t*(1+x+x^2))).
T(n,2*n) = 1, and T(n,n) = A113682(n) for n >= 0.
T(n,n-1) = A246437(n+1), and T(n,n-1)+T(n,n) = A002426(n+1) for n > 0.
If d(n) is n-th antidiagonal sum of the triangle then: d(n) = A008937(n+1), and d(n+2)-d(n) = A001590(n+5) for n >= 0.
Conjecture: If a(n) is n-th antidiagonal alternating sum of the triangle then: a(n) = A004524(n+3).
Sum_{k=0..2*n} (-1)^k*T(n,k)^2 = (3^(n+1)-1)/2 for n >= 0.
Sum_{k=0..2*n} (-1)^k*(y*k+1)*T(n,k) = Sum{k=0..n} y*k+1 = (n+1)*(y*n+2)/2 for real y and n >= 0.
Conjecture of linear recurrence for column k: Sum_{m=0..k+2} (-1)^m*T(n+m,k)* binomial(k+2,m) = 0 for k >= 0 and n >= 0.

A290561 a(n) = n + cos(n*Pi/2).

Original entry on oeis.org

1, 1, 1, 3, 5, 5, 5, 7, 9, 9, 9, 11, 13, 13, 13, 15, 17, 17, 17, 19, 21, 21, 21, 23, 25, 25, 25, 27, 29, 29, 29, 31, 33, 33, 33, 35, 37, 37, 37, 39, 41, 41, 41, 43, 45, 45, 45, 47, 49, 49, 49, 51, 53, 53, 53, 55, 57, 57, 57, 59, 61, 61, 61, 63, 65, 65, 65
Offset: 0

Views

Author

Keywords

Comments

a(n) divides A289296(n).

Crossrefs

Programs

  • Maple
    A290561:=n->n+cos(n*Pi/2): seq(A290561(n), n=0..150); # Wesley Ivan Hurt, Aug 06 2017
  • Mathematica
    a[n_] := n + Cos[n*Pi/2]; Table[a[n], {n, 0, 60}]
  • PARI
    a(n) = n + round(cos(n*Pi/2)); \\ Michel Marcus, Aug 06 2017
    
  • PARI
    Vec((x^3 + x^2 - x + 1)/((x - 1)^2*(x^2 + 1)) + O(x^100)) \\ Colin Barker, Aug 06 2017

Formula

G.f.: (x^3 + x^2 - x + 1)/((x - 1)^2*(x^2 + 1)).
a(n) = n if n == 3 (mod 4), and a(n) = a(n-4) + 4 otherwise, for n>2.
a(n) = a(n+20) - 20.
a(n) = 2*A004524(n) + 1.
a(n) + A290562(n) = 2*n.
a(n) * A290562(n) = n^2 - cos(n*Pi/2)^2 = A085046(n) for n>0.
A290562(n) = -a(-n).
From Colin Barker, Aug 06 2017: (Start)
a(n) = ((-i)^n + i^n)/2 + n where i=sqrt(-1).
a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - a(n-4) for n>3. (End)
Previous Showing 21-30 of 33 results. Next