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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A126714 Dual Wythoff array read along antidiagonals.

Original entry on oeis.org

1, 2, 4, 3, 6, 7, 5, 10, 11, 9, 8, 16, 18, 14, 12, 13, 26, 29, 23, 19, 15, 21, 42, 47, 37, 31, 24, 17, 34, 68, 76, 60, 50, 39, 27, 20, 55, 110, 123, 97, 81, 63, 44, 32, 22, 89, 178, 199, 157, 131, 102, 71, 52, 35, 25, 144, 288, 322, 254, 212, 165, 115, 84, 57, 40, 28
Offset: 1

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Author

R. J. Mathar, Feb 12 2007

Keywords

Comments

The dual Wythoff array is the dispersion of the sequence w given by w(n)=2+floor(n*x), where x=(golden ratio), so that w=2+A000201(n). For a discussion of dispersions, see A191426. - Clark Kimberling, Jun 03 2011

Examples

			Array starts
1 2 3 5 8 13 21 34 55 89 144
4 6 10 16 26 42 68 110 178 288 466
7 11 18 29 47 76 123 199 322 521 843
9 14 23 37 60 97 157 254 411 665 1076
12 19 31 50 81 131 212 343 555 898 1453
15 24 39 63 102 165 267 432 699 1131 1830
17 27 44 71 115 186 301 487 788 1275 2063
20 32 52 84 136 220 356 576 932 1508 2440
22 35 57 92 149 241 390 631 1021 1652 2673
25 40 65 105 170 275 445 720 1165 1885 3050
28 45 73 118 191 309 500 809 1309 2118 3427
		

References

  • Clark Kimberling, "Stolarsky Interspersions," Ars Combinatoria 39 (1995) 129-138. See page 135 for the dual Wythoff array and other dual arrays. - Clark Kimberling, Oct 29 2009

Crossrefs

First three rows identical to A035506. First column is A007066. First row is A000045. 2nd row is essentially A006355. 3rd row is essentially A000032. 4th row essentially A000285. 5th row essentially A013655 or A001060. 6th row essentially A022086 or A097135. 7th row essentially A022120. 8th row essentially A022087. 9th row essentially A022130. 10th row essentially A022088. 11th row essentially A022095. 12th row essentially A022089 etc.
Cf. A035513 (Wythoff array).

Programs

  • Maple
    Tn1 := proc(T,nmax,row) local n,r,c,fnd; n := 1; while true do fnd := false; for r from 1 to row do for c from 1 to nmax do if T[r,c] = n then fnd := true; fi; od; if T[r,nmax] < n then RETURN(-1); fi; od; if fnd then n := n+1; else RETURN(n); fi; od; end; Tn2 := proc(T,nmax,row,ai1) local n,r,c,fnd; for r from 1 to row do for c from 1 to nmax do if T[r,c]+1 = ai1 then RETURN(T[r,c+1]+1); fi; od; od; RETURN(-1); end; T := proc(nmax) local a,col,row; a := array(1..nmax,1..nmax); for col from 1 to nmax do a[1,col] := combinat[fibonacci](col+1); od; for row from 2 to nmax do a[row,1] := Tn1(a,nmax,row-1); a[row,2] := Tn2(a,nmax,row-1,a[row,1]); for col from 3 to nmax do a[row,col] := a[row,col-2]+a[row,col-1]; od; od; RETURN(a); end; nmax := 12; a := T(nmax); for d from 1 to nmax do for row from 1 to d do printf("%d, ",a[row,d-row+1]); od; od;
  • Mathematica
    (* program generates the dispersion array T of the complement of increasing sequence f[n] *)
    r = 40; r1 = 12;  (* r=# rows of T, r1=# rows to show *)
    c = 40; c1 = 12;   (* c=# cols of T, c1=# cols to show *)
    x = GoldenRatio; f[n_] := Floor[n*x + 2]
    (* f(n) is complement of column 1 *)
    mex[list_] := NestWhile[#1 + 1 &, 1, Union[list][[#1]] <= #1 &, 1, Length[Union[list]]]
    rows = {NestList[f, 1, c]};
    Do[rows = Append[rows, NestList[f, mex[Flatten[rows]], r]], {r}];
    t[i_, j_] := rows[[i, j]];  (* the array T *)
    TableForm[Table[t[i, j], {i, 1, 10}, {j, 1,10}]]
    (* Dual Wythoff array, A126714 *)
    Flatten[Table[t[k, n - k + 1], {n, 1, c1}, {k, 1, n}]] (* array as a sequence *)
    (* Program by Peter J. C. Moses, Jun 01 2011; added here by Clark Kimberling, Jun 03 2011 *)

A187890 a(1) = 0, a(2) = 4, a(n) = a(n-1) + a(n-2) - 1.

Original entry on oeis.org

0, 4, 3, 6, 8, 13, 20, 32, 51, 82, 132, 213, 344, 556, 899, 1454, 2352, 3805, 6156, 9960, 16115, 26074, 42188, 68261, 110448, 178708, 289155, 467862, 757016, 1224877, 1981892, 3206768, 5188659, 8395426, 13584084, 21979509, 35563592, 57543100
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Mathematica
    Join[{a = 0, b = 4}, Table[c = a+b-1; a=b; b=c, {n, 100}]]
    LinearRecurrence[{2, 0, -1}, {0, 4, 3}, 40] (* Harvey P. Dale, Sep 25 2013 *)
    CoefficientList[Series[(-x (-4 + 5 x))/((x - 1) (x^2 + x - 1)), {x, 0, 40}], x] (* Vincenzo Librandi, Sep 26 2013 *)

Formula

G.f.: -x^2*(-4+5*x) / ( (x-1)*(x^2+x-1) ). - R. J. Mathar, Mar 15 2011
a(n) = 1+A001060(n-2), n>2. - R. J. Mathar, Mar 15 2011
a(n) - a(n-1) = A013655(n-4). - R. J. Mathar, Jun 19 2021
If we start the sequence 1, 3, 6, ... and set the offset to 0, then the sequence has the generating function (1 + x - 3*x^3)/(x^3 - 2*x + 1) and gives the row sums of A374438. - Peter Luschny, Jul 22 2024

Extensions

Definition adapted to offset by Georg Fischer, Jun 19 2021

A244472 2nd-largest term in n-th row of Stern's diatomic triangle A002487.

Original entry on oeis.org

1, 2, 4, 7, 12, 19, 31, 50, 81, 131, 212, 343, 555, 898, 1453, 2351, 3804, 6155, 9959, 16114, 26073, 42187, 68260, 110447, 178707, 289154, 467861, 757015, 1224876, 1981891, 3206767, 5188658, 8395425, 13584083, 21979508, 35563591, 57543099
Offset: 1

Views

Author

N. J. A. Sloane, Jul 01 2014

Keywords

Crossrefs

Cf. A002487, A013655, A100545 (bisection).

Programs

  • Magma
    I:=[1, 2, 4, 7, 12]; [n le 5 select I[n] else Self(n-1)+Self(n-2): n in [1..40]]; // Wesley Ivan Hurt, Jul 10 2015
  • Maple
    A244472 := proc(n)
        if n < 4 then
            op(n,[1,2,4]) ;
        else
            combinat[fibonacci](n+2)-combinat[fibonacci](n-3) ;
        end if;
    end proc:
    seq(A244472(n),n=1..50) ; # R. J. Mathar, Jul 05 2014
  • Mathematica
    CoefficientList[Series[-(x^4 + x^3 + x^2 + x + 1)/(x^2 + x - 1), {x, 0, 50}], x] (* Wesley Ivan Hurt, Jul 10 2015 *)
    Join[{1, 2, 4}, LinearRecurrence[{1, 1}, {7, 12}, 50]] (* Vincenzo Librandi, Jul 11 2015 *)
  • PARI
    Vec(-x*(x^4+x^3+x^2+x+1)/(x^2+x-1) + O(x^100)) \\ Colin Barker, Jul 10 2015
    

Formula

a(n) = A013655(n-1), n>3.
a(n) = a(n-1)+a(n-2), n>5. - Colin Barker, Jul 10 2015
G.f.: -x*(x^4+x^3+x^2+x+1) / (x^2+x-1). - Colin Barker, Jul 10 2015

A022318 a(n) = a(n-1) + a(n-2) + 1, with a(0) = 1 and a(1) = 4.

Original entry on oeis.org

1, 4, 6, 11, 18, 30, 49, 80, 130, 211, 342, 554, 897, 1452, 2350, 3803, 6154, 9958, 16113, 26072, 42186, 68259, 110446, 178706, 289153, 467860, 757014, 1224875, 1981890, 3206766, 5188657, 8395424
Offset: 0

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Author

Keywords

Crossrefs

Cf. A122195.

Programs

  • Mathematica
    LinearRecurrence[{2,0,-1}, {1,4,6}, 50] (* G. C. Greubel, Aug 25 2017 *)
  • PARI
    x='x+O('x^50); Vec((1+2*x-2*x^2)/((1-x)*(1-x-x^2))) \\ G. C. Greubel, Aug 25 2017

Formula

From Ron Knott, Aug 25 2006: (Start)
a(n) = 2*A000045(n+2) + A000045(n) - 1.
G.f.: (1+2*x-2*x^2)/((1-x)*(1-x-x^2)).
a(0)=1, a(1)=4, a(2)=6, a(n) = 2*a(n-1) - a(n-3). (End)
a(n) - a(n-1) = A013655(n-1). - R. J. Mathar, May 06 2014

A153892 Primes that are the sum of five consecutive Fibonacci numbers.

Original entry on oeis.org

7, 19, 31, 131, 1453, 2351, 42187, 1981891, 3206767, 13584083, 332484016063, 66165989928299, 146028309791690867, 1619478772188347101, 47020662244482792763, 229030451631542624193448579, 1569798068858809572115420691
Offset: 1

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Author

Keywords

Comments

Primes of the form F(k+3)+L(k+2), where F(k) and L(k) are the k-th Fibonacci number and Lucas number, respectively. This formula also gives that 3,2 and 5 are primes of the form F(k+3)+L(k+2), with k=-2, k=-1, k=0, respectively. - Rigoberto Florez, Jul 31 2022
Are there infinitely many primes of the form F(k+3)+L(k+2)? There are 47 primes of this form for k <= 80000. There are no such primes for 64000 <= k <= 80000. - Rigoberto Florez, Feb 26 2023
a(29) has 948 digits; a(30) has 1253 digits. - Harvey P. Dale, Jan 13 2013

Examples

			a(1) =  7 = 0+1+1+2+3 is prime;
a(2) = 19 = 1+2+3+5+8 is prime;
a(3) = 31 = 2+3+5+8+13 is prime, etc.
		

Crossrefs

Programs

  • Mathematica
    Select[Total/@Partition[Fibonacci[Range[0,150]],5,1],PrimeQ] (* Harvey P. Dale, Jan 13 2013 *)

A210209 GCD of all sums of n consecutive Fibonacci numbers.

Original entry on oeis.org

0, 1, 1, 2, 1, 1, 4, 1, 3, 2, 11, 1, 8, 1, 29, 2, 21, 1, 76, 1, 55, 2, 199, 1, 144, 1, 521, 2, 377, 1, 1364, 1, 987, 2, 3571, 1, 2584, 1, 9349, 2, 6765, 1, 24476, 1, 17711, 2, 64079, 1, 46368, 1, 167761, 2, 121393, 1, 439204, 1, 317811, 2, 1149851, 1, 832040
Offset: 0

Views

Author

Alonso del Arte, Mar 18 2012

Keywords

Comments

Early on in the Posamentier & Lehmann (2007) book, the fact that the sum of any ten consecutive Fibonacci numbers is a multiple of 11 is presented as an interesting property of the Fibonacci numbers. Much later in the book a proof of this fact is given, using arithmetic modulo 11. An alternative proof could demonstrate that 11*F(n + 6) = Sum_{i=n..n+9} F(i).

Examples

			a(3) = 2 because all sums of three consecutive Fibonacci numbers are divisible by 2 (F(n) + F(n-1) + F(n-2) = 2F(n)), but since the GCD of 3 + 5 + 8 = 16 and 5 + 8 + 13 = 26 is 2, no number larger than 2 divides all sums of three consecutive Fibonacci numbers.
a(4) = 1 because the GCD of 1 + 1 + 2 + 3 = 7 and 1 + 2 + 3 + 5 = 11 is 1, so the sums of four consecutive Fibonacci numbers have no factors in common.
		

References

  • Alfred S. Posamentier & Ingmar Lehmann, The (Fabulous) Fibonacci Numbers, Prometheus Books, New York (2007) p. 33.

Crossrefs

Cf. A000045, A000071, sum of the first n Fibonacci numbers, A001175 (Pisano periods). Cf. also A229339.
Bisections give: A005013 (even part), A131534 (odd part).
Sums of m consecutive Fibonacci numbers: A055389 (m = 3, ignoring the initial 1); A000032 (m = 4, these are the Lucas numbers); A013655 (m = 5); A022087 (m = 6); A022096 (m = 7); A022379 (m = 8).

Programs

  • Maple
    a:= n-> (Matrix(7, (i, j)-> `if`(i=j-1, 1, `if`(i=7, [1, 0, -3, -1, 1, 3, 0][j], 0)))^iquo(n, 2, 'r'). `if`(r=0, <<0, 1, 1, 4, 3, 11, 8>>, <<1, 2, 1, 1, 2, 1, 1>>))[1, 1]: seq(a(n), n=0..80);  # Alois P. Heinz, Mar 18 2012
  • Mathematica
    Table[GCD[Fibonacci[n + 1] - 1, Fibonacci[n]], {n, 1, 50}] (* Horst H. Manninger, Dec 19 2021 *)
  • PARI
    a(n)=([0,1,0,0,0,0,0,0,0,0,0,0,0,0; 0,0,1,0,0,0,0,0,0,0,0,0,0,0; 0,0,0,1,0,0,0,0,0,0,0,0,0,0; 0,0,0,0,1,0,0,0,0,0,0,0,0,0; 0,0,0,0,0,1,0,0,0,0,0,0,0,0; 0,0,0,0,0,0,1,0,0,0,0,0,0,0; 0,0,0,0,0,0,0,1,0,0,0,0,0,0; 0,0,0,0,0,0,0,0,1,0,0,0,0,0; 0,0,0,0,0,0,0,0,0,1,0,0,0,0; 0,0,0,0,0,0,0,0,0,0,1,0,0,0; 0,0,0,0,0,0,0,0,0,0,0,1,0,0; 0,0,0,0,0,0,0,0,0,0,0,0,1,0; 0,0,0,0,0,0,0,0,0,0,0,0,0,1; 1,0,0,0,-3,0,-1,0,1,0,3,0,0,0]^n*[0;1;1;2;1;1;4;1;3;2;11;1;8;1])[1,1] \\ Charles R Greathouse IV, Jun 20 2017

Formula

G.f.: -x*(x^12-x^11+2*x^10-x^9-2*x^8-x^7-6*x^6+x^5-2*x^4+x^3+2*x^2+x+1) / (x^14-3*x^10-x^8+x^6+3*x^4-1) = -1/(x^4+x^2-1) + (x^2+1)/(x^4-x^2-1) + (x+2)/(6*(x^2+x+1)) + (x-2)/(6*(x^2-x+1)) - 2/(3*(x+1)) - 2/(3*(x-1)). - Alois P. Heinz, Mar 18 2012
a(n) = gcd(Fibonacci(n+1)-1, Fibonacci(n)). - Horst H. Manninger, Dec 19 2021
From Aba Mbirika, Jan 21 2022: (Start)
a(n) = gcd(F(n+1)-1, F(n+2)-1).
a(n) = Lcm_{A001175(m) divides n} m.
Proofs of these formulas are given in Theorems 15 and 25 of the Guyer-Mbirika paper. (End)

Extensions

More terms from Alois P. Heinz, Mar 18 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

A174562 a(1)=2, a(2)=3, then a(n)=a(n-1)+a(n-2) if n odd, a(n)=a(n-1)-a(n-2) if n even.

Original entry on oeis.org

2, 3, 5, 2, 7, 5, 12, 7, 19, 12, 31, 19, 50, 31, 81, 50, 131, 81, 212, 131, 343, 212, 555, 343, 898, 555, 1453, 898, 2351, 1453, 3804, 2351, 6155, 3804, 9959, 6155, 16114, 9959, 26073, 16114, 42187, 26073, 68260, 42187, 110447, 68260, 178707, 110447
Offset: 1

Views

Author

Giovanni Teofilatto, Mar 22 2010

Keywords

Programs

  • Mathematica
    nxt[{n_,a_,b_}]:={n+1,b,If[EvenQ[n],b-a,b+a]}; Transpose[ NestList[ nxt,{1,2,3},50]][[2]] (* or *) LinearRecurrence[{0,1,0,1},{2,3,5,2},51] (* Harvey P. Dale, Jan 06 2012 *)

Formula

a(n)= a(n-2) +a(n-4). G.f.: x*(-2-3*x-3*x^2+x^3)/(-1+x^2+x^4). a(2n+1) = A001060(n). a(2n) = A013655(n-1). [From R. J. Mathar, Apr 14 2010]

Extensions

a(44) corrected by R. J. Mathar, Apr 14 2010
Precise definition from R. J. Mathar, Aug 23 2010

A199535 Clark Kimberling's even first column Stolarsky array read by antidiagonals.

Original entry on oeis.org

1, 2, 4, 3, 7, 6, 5, 11, 9, 10, 8, 18, 15, 17, 12, 13, 29, 24, 27, 19, 14, 21, 47, 39, 44, 31, 23, 16, 34, 76, 63, 71, 50, 37, 25, 20, 55, 123, 102, 115, 81, 60, 41, 33, 22, 89, 199, 165, 186, 131, 97, 66, 53, 35, 26, 144, 322, 267, 301, 212, 157, 107, 86, 57, 43, 28
Offset: 1

Views

Author

Casey Mongoven, Nov 07 2011

Keywords

Comments

The rows of the array can be seen to have the form A(n, k) = p(n)*Fibonacci(k) + q(n)*Fibonacci(k+1) where p(n) is the sequence {0, 1, 3, 3, 3, 5, 7, 7, 9, 9, 11, 11, 13, 13, 15, 15, 17, ...}{n >= 1} and q(n) is the sequence {1, 3, 3, 7, 2, 9, 9, 13, 13, 17, 17, 19, 19, 23, 23, 25, ...}{n >= 1}. - G. C. Greubel, Jun 23 2022

Examples

			The even first column stolarsky array (EFC array), northwest corner:
  1......2.....3.....5.....8....13....21....34....55....89...144 ... A000045;
  4......7....11....18....29....47....76...123...199...322...521 ... A000032;
  6......9....15....24....39....63...102...165...267...432...699 ... A022086;
  10....17....27....44....71...115...186...301...487...788..1275 ... A022120;
  12....19....31....50....81...131...212...343...555...898..1453 ... A013655;
  14....23....37....60....97...157...254...411...665..1076..1741 ... A000285;
  16....25....41....66...107...173...280...453...733..1186..1919 ... A022113;
  20....33....53....86...139...225...364...589...953..1542..2495 ... A022096;
  22....35....57....92...149...241...390...631..1021..1652..2673 ... A022130;
Antidiagonal rows (T(n, k)):
   1;
   2,   4;
   3,   7,   6;
   5,  11,   9,  10;
   8,  18,  15,  17, 12;
  13,  29,  24,  27, 19, 14;
  21,  47,  39,  44, 31, 23, 16;
  34,  76,  63,  71, 50, 37, 25, 20;
  55, 123, 102, 115, 81, 60, 41, 33, 22;
		

Crossrefs

Formula

From G. C. Greubel, Jun 23 2022: (Start)
T(n, 1) = A000045(n+1).
T(n, 2) = A000032(n+1), n >= 2.
T(n, 3) = A022086(n) = A097135(n), n >= 3.
T(n, 4) = A022120(n-2), n >= 4.
T(n, 5) = A013655(n-1), n >= 5.
T(n, 6) = A000285(n-2), n >= 6.
T(n, 7) = A022113(n-4), n >= 7.
T(n, 8) = A022096(n-4), n >= 8.
T(n, 9) = A022130(n-6), n >= 9.
T(n, 10) = A022098(n-5), n >= 10.
T(n, 11) = A022095(n-7), n >= 11.
T(n, 12) = A022121(n-8), n >= 12.
T(n, 13) = A022388(n-10), n >= 13.
T(n, 14) = A022122(n-10), n >= 14.
T(n, 15) = A022097(n-10), n >= 15.
T(n, 16) = A022088(n-10), n >= 16.
T(n, 17) = A022390(n-14), n >= 17.
T(n, n) = A199536(n).
T(n, n-1) = A199537(n-1), n >= 2. (End)

Extensions

More terms added by G. C. Greubel, Jun 23 2022
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