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.

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A132148 Triangular array T(n,k) = C(n,k)*Lucas(n-k), 0 <= k <= n.

Original entry on oeis.org

2, 1, 2, 3, 2, 2, 4, 9, 3, 2, 7, 16, 18, 4, 2, 11, 35, 40, 30, 5, 2, 18, 66, 105, 80, 45, 6, 2, 29, 126, 231, 245, 140, 63, 7, 2, 47, 232, 504, 616, 490, 224, 84, 8, 2, 76, 423, 1044, 1512, 1386, 882, 336, 108, 9, 2, 123, 760, 2115, 3480, 3780, 2772, 1470, 480, 135, 10, 2
Offset: 0

Views

Author

Peter Bala, Aug 17 2007

Keywords

Examples

			Triangle starts
   2;
   1,   2;
   3,   2,    2;
   4,   9,    3,   2;
   7,  16,   18,   4,   2;
  11,  35,   40,  30,   5,  2;
  18,  66,  105,  80,  45,  6,  2;
  ...
		

Crossrefs

Cf. A000032 (T(n,0)), A000045, A005248 (row sums), A061084 (alter. row sums), A094440.

Programs

  • Maple
    with(combinat): lucas := n -> fibonacci(n-1) + fibonacci(n+1): T := (n,k) -> binomial(n,k)*lucas(n-k): for n from 0 to 10 do seq( T(n,k), k = 0..n) od;
  • Mathematica
    Flatten[Table[Binomial[n,k]LucasL[n-k],{n,0,10},{k,0,n}]] (* Harvey P. Dale, Nov 06 2011 *)

Formula

G.f.: (2 - (2x + 1)*t)/(1 - (2x + 1)*t + (x^2 + x - 1)*t^2) = 2 + (1 + 2*x)*t + (3 + 2*x + 2*x^2)*t^2 + (4 + 9*x + 3*x^2 + 2*x^3)*t^3 + ... .
The row polynomials L(n,x) = Sum_{k = 0..n} C(n,k)*Lucas(n-k)*x^k satisfy L(n,x)*F(n,x) = F(2*n,x), where F(n,x) = Sum_{k = 0..n} C(n,k)*Fibonacci(n-k)*x^k.
Other identities and formulas include:
L(n+1,x)^2 - L(n,x)*L(n+2,x) = -5*(x^2 + x - 1)^n;
L(n+1,x) - (x^2 + x - 1)*L(n-1,x) = 5*F(n,x) for n >= 1;
L(2*n,x) - 2*(x^2 + x - 1)^n = 5*F(n,x)^2;
L(n,2*x) = Sum_{ k = 0..n} C(n,k)*L(n-k,x)*x^k;
L(n,3*x) = Sum_{ k = 0..n} C(n,k)*L(n-k,2*x)*x^k etc.
Sum_{k = 0..n} C(n,k)*L(k,x)*F(n-k,x) = 2^n*F(n,x).
Row sums: L(n,1) = Lucas(2*n); Alternating row sums: L(n,-1) = (-1)^n*Lucas(n); L(n,1/phi) = (-1)^n*L(n,-phi) = sqrt(5)^n for n >= 1, where phi = (1 + sqrt(5))/2.
The polynomials L(n,-x) satisfy a Riemann hypothesis: the zeros of L(n,-x) lie on the vertical line Re x = 1/2 in the complex plane.
From Peter Bala, Jun 29 2016: (Start)
L(n,x) = (x + phi)^n + (x - 1/phi)^n, where phi = (1 + sqrt(5))/2. The zeros of L(n,x) are given by -1/2 - i*sqrt(5)/2*cot( (2*k - 1)*Pi/(2*n) ) for k = 1..n.
d/dx(L(n,x)) = n*L(n-1,x).
L(-n,x) = L(n,x)/(x^2 + x - 1)^n.
L(n,x - 1) = (-1)^n*L(n,-x).
L(n,x)^2 - L(2*n,x) = 2*(x^2 + x - 1)^n.
L(n,x)^3 - L(3*n,x) = 3*(x^2 + x - 1)^n*L(n,x).
L(n,x)^4 - L(4*n,x) = 4*(x^2 + x - 1)^n*L(n,x)^2 - 2*(x^2 + x - 1)^(2*n).
If n divides m and m/n is odd then L(n,x) divides L(m,x) in the polynomial ring Z[x].
L(n,x) = F(n+1,x) - (x^2 + x - 1)*F(n-1,x) = 2*F(n+1,x) - (2*x + 1)*F(n,x), where F(n,x) = Sum_{k = 0..n} binomial(n,k)*Fibonacci(n-k)*x^k denotes the n-th row polynomial of A094440 (taken with an offset of 0).
exp( Sum_{n >= 1} L(n,x)*z^n/n ) = Sum_{n >= 0} F(n+1,x)*z^n.
exp( Sum_{n >= 1} L(n,x)*L(2*n,x)*z^n/n ) = 1/( F(1,x)*F(2*x)*F(3,x) ) * Sum_{n >= 0} F(n+1,x)*F(n+2,x)* F(n+3,x)*z^n. (End)
From Peter Bala, Dec 31 2023: (Start)
For n >= 1, the n-th row polynomial L(n,x) is the numerator of 1/(n-1)! * (d/dx)^(n-1) (2*x + 1)/(1 - x - x^2).
Recurrence: for n >= 1, n*L(n+1,x) = n*(2*x + 1)*L(n,x) + (1 - x - x^2)* d/dx(L(n,x)) with L(1,x) = 2*x + 1. (End)

A061083 Fibonacci-type sequence based on division: a(0) = 1, a(1) = 2 and a(n) = a(n-2)/a(n-1) but ignore decimal point.

Original entry on oeis.org

1, 2, 5, 4, 125, 32, 390625, 8192, 476837158203125, 17179869184, 277555756156289135105907917022705078125, 618970019642690137449562112
Offset: 0

Views

Author

Ulrich Schimke (ulrschimke(AT)aol.com)

Keywords

Examples

			a(6) = 390625, since a(4)/a(5) = 125/32 = 3.90625
		

Crossrefs

Cf. A061084 for subtraction, A000301 for multiplication and A000045 for addition - the common Fibonacci numbers

Programs

  • Haskell
    a061083 n = a061083_list !! n
    a061083_list = 1 : 2 : zipWith divIgnPnt a061083_list (tail a061083_list)
       where divIgnPnt x y = ddiv (10 * m) x' where
                ddiv u w | r == 0    = 10 * w + q
                         | otherwise = ddiv (10 * r) (10 * w + q)
                         where (q,r) = divMod u y
                (x',m) = divMod x y
    -- Reinhard Zumkeller, Dec 29 2011

Formula

a(n) = k^(n-th Fibonacci number) with k=2 if n is odd, k=5 if n is even

A083564 a(n) = L(n)*L(2n), where L(n) are the Lucas numbers (A000204).

Original entry on oeis.org

3, 21, 72, 329, 1353, 5796, 24447, 103729, 439128, 1860621, 7880997, 33385604, 141421803, 599075421, 2537719272, 10749959329, 45537545553, 192900159396, 817138154247, 3461452823129, 14662949371128, 62113250430021
Offset: 1

Views

Author

Gary W. Adamson, Jun 12 2003

Keywords

Comments

a(n+1)/a(n) -> (phi)^3 = ((1 + sqrt(5))/2)^3 = 4.236067...

Examples

			a(4) = Lucas(4)*Lucas(8) = 7*47 = 329.
		

Crossrefs

Third row of array A028412.

Programs

Formula

From Benoit Cloitre, Aug 30 2003: (Start)
a(n) = 3*a(n-1) + 6*a(n-2) - 3*a(n-3) - a(n-4);
a(n) = Fibonacci(4*n)/Fibonacci(n) = A000045(4*n)/A000045(n). (End)
a(n) = Lucas(3*n) + (-1)^n*Lucas(n).
From R. J. Mathar, Oct 27 2008: (Start)
G.f.: x*(3+12*x-9*x^2-4*x^3)/((1+x-x^2)*(1-4*x-x^2)).
a(n) = A061084(n+1) + 2*A001077(n). (End)
a(n) = (1+phi)^n + (-phi)^n + (2*phi+1)^n + (3-2*phi)^n, phi = (1+sqrt(5))/2. - Gary Detlefs, Dec 09 2012

A099255 Expansion of g.f. (7+6*x-6*x^2-3*x^3)/((x^2+x-1)*(x^2-x-1)).

Original entry on oeis.org

7, 6, 15, 15, 38, 39, 99, 102, 259, 267, 678, 699, 1775, 1830, 4647, 4791, 12166, 12543, 31851, 32838, 83387, 85971, 218310, 225075, 571543, 589254, 1496319, 1542687, 3917414, 4038807, 10255923, 10573734, 26850355, 27682395, 70295142, 72473451
Offset: 0

Views

Author

Creighton Dement, Oct 09 2004

Keywords

Comments

One of two sequences involving the Lucas/Fibonacci numbers.
This sequence consists of pairs of numbers more or less close to each other with "jumps" in between pairs. "pos((Ex)^n)" sums up over all floretion basis vectors with positive coefficients for each n. The following relations appear to hold: a(2n) - (a(2n-1) + a(2n-2)) = 2*Luc(2n) a(2n+1) - a(2n) = Fib(2n), apart from initial term a(2n+1)/a(2n-1) -> 2 + golden ratio phi a(2n)/a(2n-2) -> 2 + golden ratio phi An identity: (1/2)a(n) - (1/2)A099256(n) = ((-1)^n)A000032(n)

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{0,3,0,-1},{7,6,15,15},40] (* Harvey P. Dale, Dec 29 2012 *)

Formula

a(n) = 2*pos((Ex)^n)
a(0) = 7, a(1) = 6, a(2) = a(3) = 15, a(n+4) = 3a(n+2) - a(n).
a(2n) = A022097(2n+1), a(2n+1) = A022086(2n+3).
a(n) = A061084(n+1)+A013655(n+2). [R. J. Mathar, Nov 30 2008]

Extensions

More terms from Creighton Dement, Apr 19 2005

A099256 Expansion of g.f. (3-x)*(1+3*x+x^2)/((1-x-x^2)*(1+x-x^2)).

Original entry on oeis.org

3, 8, 9, 23, 24, 61, 63, 160, 165, 419, 432, 1097, 1131, 2872, 2961, 7519, 7752, 19685, 20295, 51536, 53133, 134923, 139104, 353233, 364179, 924776, 953433, 2421095, 2496120, 6338509, 6534927, 16594432, 17108661, 43444787, 44791056, 113739929, 117264507, 297775000, 307002465, 779585071
Offset: 0

Views

Author

Creighton Dement, Oct 18 2004

Keywords

Comments

One of two sequences involving the Lucas/Fibonacci numbers. This sequence consists of pairs of numbers more or less close to each other with "jumps" in between pairs.
a(n+3) + a(n) - a(n+2) appears to be mysteriously connected with a(n+1).
Both this sequence and A099255 were created using "Floretion dynamical symmetries" (see link for further details).

Crossrefs

Cf. A000045, A099255, A000032, A055273 (bisection), A097134 (bisection).

Programs

  • Mathematica
    LinearRecurrence[{0,3,0,-1},{3,8,9,23},40] (* Harvey P. Dale, Apr 22 2012 *)

Formula

a(2n+2) - a(2n+1) = Fibonacci(2n-1).
A099255(n)/2 - a(n)/2 = (-1)^n*A000032(n)
a(0) = 3, a(1) = 8, a(2) = 9, a(3) = 23, a(n+4) = 3a(n+2) - a(n).
a(2n) = A022086(2n+2), a(2n+1) = A022097(2n+2).
a(n) = A013655(n+2)-A061084(n+1).

Extensions

Definition corrected, extended. - R. J. Mathar, Nov 13 2008

A190914 Expansion of ( 5-9*x^2-2*x^3 ) / ( (1+x-x^2)*(1-x-x^2-x^3) ).

Original entry on oeis.org

5, 0, 6, 3, 18, 10, 57, 42, 178, 165, 566, 616, 1821, 2236, 5914, 7963, 19362, 27982, 63813, 97394, 211458, 336633, 703786, 1157544, 2350597, 3964960, 7872702, 13541691, 26425522, 46147178, 88853297, 156994354, 299165378, 533410837, 1008343310, 1810544592, 3401446413, 6140811708, 11481472994, 20815538227
Offset: 0

Views

Author

Reikku Kulon, May 23 2011

Keywords

Comments

The sequence ..., 14, 29, 10, 2, 9, 2, 0, [5], 0, 6, 3, 18, 10, 57, 42, ...
(the number in square brackets at index 0) equals the trace of:
[ 0 0 0 0-1 ]
[ 1 0 0 0 0 ]
[ 0 1 0 0 1 ]^(+n)
[ 0 0 1 0 3 ]
[ 0 0 0 1 0 ]
or
[ 0 0 0 0-1 ]
[ 1 0 0 0 0 ]
[ 0 1 0 0 3 ]^(-n)
[ 0 0 1 0 1 ]
[ 0 0 0 1 0 ]
Its characteristic polynomial is (x^2 +/- x - 1) * (x^3 -/+ x^2 -/+ x - 1); these factors are Fibonacci and tribonacci polynomials. The ratio of negative terms approaches the golden ratio; the ratio of positive terms approaches the tribonacci constant.
Prime numbers p divide a(+p) and a(-p), as the trace of a matrix M^p (mod p) is constant.
Nonprimes c very rarely divide a(+c) and a(-c) simultaneously. The only known dual pseudoprime in the sequence is 1.
The distribution of residues induces gaps between pseudoprimes having roughly the size of c. For example, after 1034881 there is a gap of more than one million terms without either variety of pseudoprime.
Pseudoprimes appear limited to squared primes and squarefree numbers with three or more prime factors. 11 and 13 are more common than other factors.
Positive pseudoprimes: c | a(+c)
----------------------------------------------
1
3481. . . . 59^2
17143 . . . 7 31 79
105589. . . 11 29 331
635335. . . 5 283 449
2992191 . . 3 29 163 211
3659569 . . 1913^2
Negative pseudoprimes: c | a(-c)
----------------------------------------------
1
9 . . . . . 3^2
806 . . . . 2 13 31
1419. . . . 3 11 43
6241. . . . 79^2
6721. . . . 11 13 47
12749 . . . 11 19 61
21106 . . . 2 61 173
38714 . . . 2 13 1489
146689. . . 383^2
649621. . . 7 17 53 103
1034881 . . 41 43 587

Crossrefs

Cf. A190913 (extended to negative indices), A000045, A000073, A001608, A000040, A005117, A125666.

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (5-9*x^2 -2*x^3)/((1+x-x^2)*(1-x-x^2-x^3)) )); // G. C. Greubel, Apr 23 2019
    
  • Mathematica
    LinearRecurrence[{0, 3, 1, 0, -1}, {5, 0, 6, 3, 18}, 40] (* G. C. Greubel, Apr 23 2019 *)
  • PARI
    my(x='x+O('x^40)); Vec((5-9*x^2-2*x^3)/((1+x-x^2)*(1-x-x^2-x^3))) \\ G. C. Greubel, Apr 23 2019
    
  • SageMath
    ((5-9*x^2-2*x^3)/((1+x-x^2)*(1-x-x^2-x^3))).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 23 2019

Formula

a(n) = A061084(n+1) + A001644(n). - R. J. Mathar, Jun 06 2011

A365907 Smallest nonnegative integer that is not the sum of fewer than n signed Lucas numbers.

Original entry on oeis.org

0, 1, 5, 16, 63, 262, 1105, 4676, 19803, 83882, 355325, 1505176, 6376023, 27009262, 114413065, 484661516, 2053059123, 8696898002, 36840651125, 156059502496, 661078661103, 2800374146902, 11862575248705, 50250675141716, 212865275815563, 901711778403962
Offset: 0

Views

Author

Mike Speciner, Sep 22 2023

Keywords

Comments

Signed Lucas numbers are the union of A000032 and A061084.

Examples

			a(0) = 0, the sum of 0 Lucas numbers.
a(1) = 1 = A000032(1), the sum of 1 Lucas number.
a(2) = 5 = 1+4 = A000032(1)+A000032(3), the sum of 2 Lucas numbers. (2, 3, and 4 need only one term, since they are Lucas numbers.)
a(4) = 63 = 1+4+11+47.
For comparison, 45 is the first sum requiring 4 positive Lucas numbers (45 = 1+4+11+29, see A004146), but here 45 = 47+2-4 requires only 3 signed Lucas numbers so that a(4) != 45.
		

Crossrefs

Cf. A000032, A061084, A004146 (analogous with only positive Lucas numbers).

Programs

  • Mathematica
    LinearRecurrence[{5, -3, -1}, {0, 1, 5, 16, 63}, 26] (* Amiram Eldar, Sep 26 2023 *)
  • Python
    from sympy import lucas
    a = lambda n: n if n<2 else (lucas(3*n-2)+3)//2

Formula

a(n) = n, for n<2.
a(n) = (A000032(3*n-2)+3)/2 = 1+4+Sum_{i=2..n-1} A000032(3*n-1), for n>1.
G.f.: x*(1 - 6*x^2 - x^3)/((1 - x)*(1 - 4*x - x^2)). - Stefano Spezia, Sep 25 2023

A226377 Lucas numbers differences triangle T(n,k), k<=n, where column k+1 holds the k-th differences of A000204, read by rows.

Original entry on oeis.org

1, 3, 2, 4, 1, -1, 7, 3, 2, 3, 11, 4, 1, -1, -4, 18, 7, 3, 2, 3, 7, 29, 11, 4, 1, -1, -4, -11, 47, 18, 7, 3, 2, 3, 7, 18, 76, 29, 11, 4, 1, -1, -4, -11, -29, 123, 47, 18, 7, 3, 2, 3, 7, 18, 47, 199, 76, 29, 11, 4, 1, -1, -4, -1, -29, -76, -199
Offset: 1

Views

Author

Richard R. Forberg, Jul 31 2013

Keywords

Comments

Consecutive columns (i.e. k =1,2,3...) shift the Lucas sequence (A000204) down by 2 indices.
Diagonal (n=k) produces A061084, and Lucas numbers at increasingly negative indices for n=k>2.
Row sums equal A203976(n) for n=>1, which equals Lucas numbers A000204(n) if n is odd, and 5 * A000045(2*n) (Fibonacci) if n is even.
Compare A227431 which is a differences triangle for the Fibonacci sequence A000045.

Examples

			Triangle begins:
1;
3,  2;
4,  1, -1;
7,  3,  2,  3;
11,  4,  1, -1, -4;
18,  7,  3,  2,  3,  7;
29, 11,  4,  1, -1, -4, -11;
47, 18,  7,  3,  2,  3,   7,  18;
76, 29, 11,  4,  1, -1,  -4, -11, -29;
...
		

Crossrefs

Formula

T(n,1) = A000204(n) for n>0, T(n,k) = T(n,k-1) - T(n-1,k-1).

A226447 Expansion of (1-x+x^3)/(1-x^2+2*x^3-x^4).

Original entry on oeis.org

1, -1, 1, -2, 4, -5, 9, -15, 23, -38, 62, -99, 161, -261, 421, -682, 1104, -1785, 2889, -4675, 7563, -12238, 19802, -32039, 51841, -83881, 135721, -219602, 355324, -574925, 930249, -1505175, 2435423, -3940598, 6376022, -10316619, 16692641, -27009261, 43701901, -70711162, 114413064, -185124225
Offset: 0

Views

Author

Paul Curtz, Jun 28 2013

Keywords

Comments

a(n) and its differences:
. 1, -1, 1, -2, 4, -5, 9, -15, 23, -38, ...
. -2, 2, -3, 6, -9, 14, -24, 38, -61, 100, ...
. 4, -5, 9, -15, 23, -38, 62, -99, 161, -261, ...
. -9, 14, -24, 38, -61, 100, -161, 260, -422, 682, ...
. 23, -38, 62, -99, 161, -261, 421, -682, 1104, -1785, ...
. -61, 100, -161, 260, -422, 682, -1103, 1786, -2889, 4674, ...
. 161, -261, 421, -682, 1104, -1785, 2889, -4675, 7563, -12238, ...
The third row is the first shifted .
The main diagonal is A001077(n). The fourth is -A001077(n+1). By "shifted" antidiagonals there are one 1, two 2's (-2 of the first row and 2), generally A001651(n) (-1)^n *A001077(n).
a(n+1)/a(n) tends to A001622 (the golden ratio) as n -> infinity.

Programs

  • Magma
    m:=50; R:=PowerSeriesRing(Integers(), m); Coefficients(R!((1-x+x^3)/(1-x^2+2*x^3-x^4))); // Bruno Berselli, Jul 04 2013
  • Mathematica
    a[0] = 1; a[1] = -1; a[n_] := a[n] = a[n-2] - a[n-1] - {-1, 0, 1, 1, 0, -1}[[Mod[n+1, 6] + 1]]; Table[a[n], {n, 0, 41}] (* Jean-François Alcover, Jul 04 2013 *)

Formula

a(0)=1, a(1)=-1; for n>1, a(n) = a(n-2) - a(n-1) + A010892(n+2).
a(n) = a(n-2) -2*a(n-3) +a(n-4).
a(n) = A226956(-n).
a(n+1) = A039834(n) - (-1)^n*A094686(n).
a(n+6) - a(n) = 2*(-1)^n* A000032(n+3).
a(2n+1) = -A226956(2n+1).
G.f. ( -1+x-x^3 ) / ( (x^2-x-1)*(1-x+x^2) ). - R. J. Mathar, Jun 29 2013
2*a(n) = A010892(n+2)+A061084(n+1). - R. J. Mathar, Jun 29 2013

A367816 Number of terms in a shortest sequence of Lucas numbers that sum to n, allowing Lucas numbers with negative indices.

Original entry on oeis.org

0, 1, 1, 1, 1, 2, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 3, 2, 1, 2, 2, 2, 2, 3, 3, 2, 3, 3, 2, 1, 2, 2, 2, 2, 3, 3, 2, 3, 3, 3, 2, 3, 3, 2, 3, 3, 2, 1, 2, 2, 2, 2, 3, 3, 2, 3, 3, 3, 2, 3, 3, 3, 3, 4, 3, 2, 3, 3, 3, 3, 4, 3, 2, 3, 3, 2, 1, 2, 2, 2
Offset: 0

Views

Author

Mike Speciner, Dec 01 2023

Keywords

Examples

			For n = 0, the empty sequence sums to 0, so a(0) = 0.
For n = 1, 2, 3, 4, 7, 11, 18, each n is a Lucas number, so a(n) = 1.
The first n needing a negative-index Lucas number is 17 = 18 + -1; a(17) = 2.
		

Crossrefs

Cf. A000032 Lucas numbers; A061084 negative index Lucas numbers.
A116543 is the similar sequence where negative index Lucas numbers are not allowed.
a(A365907(n)) is the first occurrence of n.

Programs

  • Python
    from itertools import count
    def  a(n) :
      """For integer n, the least number of Lucas terms required to sum to n."""
      f = [2,1];    # Lucas numbers, starting with Lucas(0)
      while f[-1] <= (n or 1) :
        f.append(f[-2]+f[-1]);
      a = [0 for _ in range(f[-1]+1)];
      for i in f :
        a[i] = 1;
      for c in count(2) :
        if not all(a[4:]) :
          for i in range(4,f[-1]) :
            if not a[i] :
              for j in f :
                if j >= i :
                  break;
                if a[i-j] == c-1 :
                  a[i] = c;
                  break;
              if not a[i]:
                for j in f[1::2] :
                  if i+j >= len(a) :
                    break;
                  if a[i+j] == c-1 :
                    a[i] = c;
                    break;
        else :
          break;
      return a[n];

Formula

a(0) = 0; a(A000032(n)) = 1.
For n > 0, a(n) = 1+min(a(n-Lucas(k))) where k ranges over Z.
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