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.

Showing 1-6 of 6 results.

A119537 Determinant of n X n matrices of first n^2 denumerants (A000115).

Original entry on oeis.org

1, 0, -3, -3, 0, -54, 343, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Jonathan Vos Post, May 28 2006

Keywords

Comments

Conjecture: a(n>7)=0. - Robert G. Wilson v, Jun 07 2006

Examples

			a(6) = -54 = -2 * 3^3. a(7) = 343 = 7^3.
a(8) = 0 because of the singular matrix 0 =
|..1...1...2...2...3...4...5...6|
|..7...8..10..11..13..14..16..18|
|.20..22..24..26..29..31..34..36|
|.39..42..45..48..51..54..58..61|
|.65..68..72..76..80..84..88..92|
|.97.101.106.110.115.120.125.130|
|135.140.146.151.157.162.168.174|
|180.186.192.198.205.211.218.224|.
		

Crossrefs

Programs

  • Mathematica
    clst = CoefficientList[ Series[1/((1 - x)(1 - x^2)(1 - x^5)), {x, 0, 105^2 - 1}], x];
    f[n_] := Det[ Partition[ Take[clst, n^2], n]];
    Array[f,100] (* Robert G. Wilson v, Jun 07 2006 *)

Formula

a(n) = determinant[A000115(k) from k=1 to n^2].

Extensions

More terms from Robert G. Wilson v, Jun 07 2006

A211422 Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w^2 + x*y = 0.

Original entry on oeis.org

1, 9, 17, 25, 41, 49, 57, 65, 81, 105, 113, 121, 137, 145, 153, 161, 193, 201, 225, 233, 249, 257, 265, 273, 289, 329, 337, 361, 377, 385, 393, 401, 433, 441, 449, 457, 505, 513, 521, 529, 545, 553, 561, 569, 585, 609, 617, 625, 657, 713, 753, 761
Offset: 0

Views

Author

Clark Kimberling, Apr 10 2012

Keywords

Comments

Suppose that S={-n,...,0,...,n} and that f(w,x,y,n) is a function, where w,x,y are in S. The number of ordered triples (w,x,y) satisfying f(w,x,y,n)=0, regarded as a function of n, is a sequence t of nonnegative integers. Sequences such as t/4 may also be integer sequences for all except certain initial values of n. In the following guide, such sequences are indicated in the related sequences column and may be included in the corresponding Mathematica programs.
...
sequence... f(w,x,y,n) ..... related sequences
A211415 ... w^2+x*y-1 ...... t+2, t/4, (t/4-1)/4
A211422 ... w^2+x*y ........ (t-1)/8, A120486
A211423 ... w^2+2x*y ....... (t-1)/4
A211424 ... w^2+3x*y ....... (t-1)/4
A211425 ... w^2+4x*y ....... (t-1)/4
A211426 ... 2w^2+x*y ....... (t-1)/4
A211427 ... 3w^2+x*y ....... (t-1)/4
A211428 ... 2w^2+3x*y ...... (t-1)/4
A211429 ... w^3+x*y ........ (t-1)/4
A211430 ... w^2+x+y ........ (t-1)/2
A211431 ... w^3+(x+y)^2 .... (t-1)/2
A211432 ... w^2-x^2-y^2 .... (t-1)/8
A003215 ... w+x+y .......... (t-1)/2, A045943
A202253 ... w+2x+3y ........ (t-1)/2, A143978
A211433 ... w+2x+4y ........ (t-1)/2
A211434 ... w+2x+5y ........ (t-1)/4
A211435 ... w+4x+5y ........ (t-1)/2
A211436 ... 2w+3x+4y ....... (t-1)/2
A211435 ... 2w+3x+5y ....... (t-1)/2
A211438 ... w+2x+2y ....... (t-1)/2, A118277
A001844 ... w+x+2y ......... (t-1)/4, A000217
A211439 ... w+3x+3y ........ (t-1)/2
A211440 ... 2w+3x+3y ....... (t-1)/2
A028896 ... w+x+y-1 ........ t/6, A000217
A211441 ... w+x+y-2 ........ t/3, A028387
A182074 ... w^2+x*y-n ...... t/4, A028387
A000384 ... w+x+y-n
A000217 ... w+x+y-2n
A211437 ... w*x*y-n ........ t/4, A007425
A211480 ... w+2x+3y-1
A211481 ... w+2x+3y-n
A211482 ... w*x+w*y+x*y-w*x*y
A211483 ... (n+w)^2-x-y
A182112 ... (n+w)^2-x-y-w
...
For the following sequences, S={1,...,n}, rather than
{-n,...,0,...n}. If f(w,x,y,n) is linear in w,x,y,n, then the sequence is a linear recurrence sequence.
A132188 ... w^2-x*y
A211506 ... w^2-x*y-n
A211507 ... w^2-x*y+n
A211508 ... w^2+x*y-n
A211509 ... w^2+x*y-2n
A211510 ... w^2-x*y+2n
A211511 ... w^2-2x*y ....... t/2
A211512 ... w^2-3x*y ....... t/2
A211513 ... 2w^2-x*y ....... t/2
A211514 ... 3w^2-x*y ....... t/2
A211515 ... w^3-x*y
A211516 ... w^2-x-y
A211517 ... w^3-(x+y)^2
A063468 ... w^2-x^2-y^2 .... t/2
A000217 ... w+x-y
A001399 ... w-2x-3y
A211519 ... w-2x+3y
A008810 ... w+2x-3y
A001399 ... w-2x-3y
A008642 ... w-2x-4y
A211520 ... w-2x+4y
A211521 ... w+2x-4y
A000115 ... w-2x-5y
A211522 ... w-2x+5y
A211523 ... w+2x-5y
A211524 ... w-3x-5y
A211533 ... w-3x+5y
A211523 ... w+3x-5y
A211535 ... w-4x-5y
A211536 ... w-4x+5y
A008812 ... w+4x-5y
A055998 ... w+x+y-2n
A074148 ... 2w+x+y-2n
A211538 ... 2w+2x+y-2n
A211539 ... 2w+2x-y-2n
A211540 ... 2w-3x-4y
A211541 ... 2w-3x+4y
A211542 ... 2w+3x-4y
A211543 ... 2w-3x-5y
A211544 ... 2w-3x+5y
A008812 ... 2w+3x-5y
A008805 ... w-2x-2y (repeated triangular numbers)
A001318 ... w-2x+2y
A000982 ... w+x-2y
A211534 ... w-3x-3y
A211546 ... w-3x+3y (triply repeated triangular numbers)
A211547 ... 2w-3x-3y (triply repeated squares)
A082667 ... 2w-3x+3y
A055998 ... w-x-y+2
A001399 ... w-2x-3y+1
A108579 ... w-2x-3y+n
...
Next, S={-n,...-1,1,...,n}, and the sequence counts the cases (w,x,y) satisfying the indicated inequality. If f(w,x,y,n) is linear in w,x,y,n, then the sequence is a linear recurrence sequence.
A211545 ... w+x+y>0; recurrence degree: 4
A211612 ... w+x+y>=0
A211613 ... w+x+y>1
A211614 ... w+x+y>2
A211615 ... |w+x+y|<=1
A211616 ... |w+x+y|<=2
A211617 ... 2w+x+y>0; recurrence degree: 5
A211618 ... 2w+x+y>1
A211619 ... 2w+x+y>2
A211620 ... |2w+x+y|<=1
A211621 ... w+2x+3y>0
A211622 ... w+2x+3y>1
A211623 ... |w+2x+3y|<=1
A211624 ... w+2x+2y>0; recurrence degree: 6
A211625 ... w+3x+3y>0; recurrence degree: 8
A211626 ... w+4x+4y>0; recurrence degree: 10
A211627 ... w+5x+5y>0; recurrence degree: 12
A211628 ... 3w+x+y>0; recurrence degree: 6
A211629 ... 4w+x+y>0; recurrence degree: 7
A211630 ... 5w+x+y>0; recurrence degree: 8
A211631 ... w^2>x^2+y^2; all terms divisible by 8
A211632 ... 2w^2>x^2+y^2; all terms divisible by 8
A211633 ... w^2>2x^2+2y^2; all terms divisible by 8
...
Next, S={1,...,n}, and the sequence counts the cases (w,x,y) satisfying the indicated relation.
A211634 ... w^2<=x^2+y^2
A211635 ... w^2A211790
A211636 ... w^2>=x^2+y^2
A211637 ... w^2>x^2+y^2
A211638 ... w^2+x^2+y^2
A211639 ... w^2+x^2+y^2<=n
A211640 ... w^2+x^2+y^2>n
A211641 ... w^2+x^2+y^2>=n
A211642 ... w^2+x^2+y^2<2n
A211643 ... w^2+x^2+y^2<=2n
A211644 ... w^2+x^2+y^2>2n
A211645 ... w^2+x^2+y^2>=2n
A211646 ... w^2+x^2+y^2<3n
A211647 ... w^2+x^2+y^2<=3n
A063691 ... w^2+x^2+y^2=n
A211649 ... w^2+x^2+y^2=2n
A211648 ... w^2+x^2+y^2=3n
A211650 ... w^3A211790
A211651 ... w^3>x^3+y^3; see Comments at A211790
A211652 ... w^4A211790
A211653 ... w^4>x^4+y^4; see Comments at A211790

Examples

			a(1) counts these 9 triples: (-1,-1,1), (-1, 1,-1), (0, -1, 0), (0, 0, -1), (0,0,0), (0,0,1), (0,1,0), (1,-1,1), (1,1,-1).
		

Crossrefs

Cf. A120486.

Programs

  • Mathematica
    t[n_] := t[n] = Flatten[Table[w^2 + x*y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]
    c[n_] := Count[t[n], 0]
    t = Table[c[n], {n, 0, 70}] (* A211422 *)
    (t - 1)/8                   (* A120486 *)

A000008 Number of ways of making change for n cents using coins of 1, 2, 5, 10 cents.

Original entry on oeis.org

1, 1, 2, 2, 3, 4, 5, 6, 7, 8, 11, 12, 15, 16, 19, 22, 25, 28, 31, 34, 40, 43, 49, 52, 58, 64, 70, 76, 82, 88, 98, 104, 114, 120, 130, 140, 150, 160, 170, 180, 195, 205, 220, 230, 245, 260, 275, 290, 305, 320, 341, 356, 377, 392, 413, 434, 455, 476, 497, 518, 546
Offset: 0

Keywords

Comments

Number of partitions of n into parts 1, 2, 5, and 10.
There is a unique solution to this puzzle: "There are a prime number of ways that I can make change for n cents using coins of 1, 2, 5, 10 cents; but a semiprime number of ways that I can make change for n-1 cents and for n+1 cents." There is a unique solution to this related puzzle: "There are a prime number of ways that I can make change for n cents using coins of 1, 2, 5, 10 cents; but a 3-almost prime number of ways that I can make change for n-1 cents and for n+1 cents." - Jonathan Vos Post, Aug 26 2005

Examples

			G.f. = 1 + x + 2*x^2 + 2*x^3 + 3*x^4 + 4*x^5 + 5*x^6 + 6*x^7 + 7*x^8 + 8*x^9 + 11*x^10 + ...
		

References

  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 316.
  • G. Pólya and G. Szegő, Problems and Theorems in Analysis, Springer-Verlag, NY, 2 vols., 1972, Vol. 1, p. 1.
  • J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 152.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Haskell
    a000008 = p [1,2,5,10] where
       p _          0 = 1
       p []         _ = 0
       p ks'@(k:ks) m = if m < k then 0 else p ks' (m - k) + p ks m
    -- Reinhard Zumkeller, Dec 15 2013
    
  • Magma
    [#RestrictedPartitions(n,{1,2,5,10}):n in [0..60]]; // Marius A. Burtea, May 07 2019
  • Maple
    M:= Matrix(18, (i,j)-> if(i=j-1 and i<17) or (j=1 and member(i, [2,5,10,17,18])) or (i=18 and j=18) then 1 elif j=1 and member(i, [7,12,15]) then -1 else 0 fi); a:= n-> (M^(n+1))[18,1]; seq(a(n), n=0..51); # Alois P. Heinz, Jul 25 2008
    # second Maple program:
    a:= proc(n) local m, r; m := iquo(n, 10, 'r'); r:= r+1; ([23, 26, 35, 38, 47, 56, 65, 74, 83, 92][r]+ (3*r+ 24+ 10*m) *m) *m/6+ [1, 1, 2, 2, 3, 4, 5, 6, 7, 8][r] end: seq(a(n), n=0..100); # Alois P. Heinz, Oct 05 2008
  • Mathematica
    a[ n_] := SeriesCoefficient[ 1 / ((1 - x)(1 - x^2)(1 - x^5)(1 - x^10)), {x, 0, n}]
    a[n_, d_] := SeriesCoefficient[1/(Times@@Map[(1-x^#)&, d]), {x, 0, n}] (* general case for any set of denominations represented as a list d of coin values in cents *)
    Table[Length[FrobeniusSolve[{1,2,5,10},n]],{n,0,70}] (* Harvey P. Dale, Apr 02 2012 *)
    LinearRecurrence[{1, 1, -1, 0, 1, -1, -1, 1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1}, {1, 1, 2, 2, 3, 4, 5, 6, 7, 8, 11, 12, 15, 16, 19, 22, 25, 28}, 100] (* Vincenzo Librandi, Feb 10 2016 *)
    a[ n_] := Quotient[ With[{r = Mod[n, 10, 1]}, n^3 + 27 n^2 + (191 + 3 {4, 13, 0, 5, 8, 9, 8, 5, 0, 13}[[r]]) n + 25], 600] + 1; (* Michael Somos, Mar 06 2018 *)
    Table[Length@IntegerPartitions[n,All,{1,2,5,10}],{n,0,70}] (* Giorgos Kalogeropoulos, May 07 2019 *)
  • Maxima
    a(n):=floor(((n+17)*(2*n^2+20*n+81)+15*(n+1)*(-1)^n+120*((floor(n/5)+1)*((1+(-1)^mod(n,5))/2-floor(((mod(n,5))^2)/8))))/1200); /* Tani Akinari, Jun 21 2013 */
    
  • PARI
    {a(n) = if( n<-17, -a(-18-n), if( n<0, 0, polcoeff( 1 / ((1 - x) * (1 - x^2) * (1 - x^5) * (1 - x^10)) + x * O(x^n), n)))}; /* Michael Somos, Apr 01 2003 */
    
  • PARI
    Vec( 1/((1-x)*(1-x^2)*(1-x^5)*(1-x^10)) + O(x^66) ) \\ Joerg Arndt, Oct 02 2013
    
  • PARI
    {a(n) = my(r = (n-1)%10 + 1); (n^3 + 27*n^2 + (191 + 3*[4, 13, 0, 5, 8, 9, 8, 5, 0, 13][r])*n + 25)\600 + 1}; /* Michael Somos, Mar 06 2018 */
    

Formula

G.f.: 1 / ((1 - x) * (1 - x^2) * (1 - x^5) * (1 - x^10)). - Michael Somos, Nov 17 1999
a(n) - a(n-1) = A025810(n). - Michael Somos, Dec 15 2002
a(n) = a(n-2) + a(n-5) - a(n-7) + a(n-10) - a(n-12) - a(n-15) + a(n-17) + 1. - Michael Somos, Apr 01 2003
a(n) = -a(-18-n). - Michael Somos, Apr 01 2003
a(n) = (q+1)*(h(n) - q*(3n-10q+7)/6) with q = floor(n/10) and h(n) = A000115(n) = round((n+4)^2/20). See link "Derivation of formulas". - Gerhard Kirchner, Feb 10 2017
a(n) = floor((2*n^3 + 54*n^2 + 421*n + 15*n*(-1)^n + 24*n * ((-1)^[(n mod 5)>2] - [(n mod 5)=1]) + 1248)/1200). - Hoang Xuan Thanh, Jun 27 2025

A001304 Expansion of 1/((1-x)^2*(1-x^2)*(1-x^5)).

Original entry on oeis.org

1, 2, 4, 6, 9, 13, 18, 24, 31, 39, 49, 60, 73, 87, 103, 121, 141, 163, 187, 213, 242, 273, 307, 343, 382, 424, 469, 517, 568, 622, 680, 741, 806, 874, 946, 1022, 1102, 1186, 1274, 1366, 1463, 1564, 1670, 1780, 1895, 2015, 2140, 2270, 2405, 2545, 2691, 2842
Offset: 0

Keywords

Comments

Ways of making change for n cents using coins of 1, 2 and 5 cents, if two different kinds of 1-cent coin are counted as different. - Matthew Vandermast, Feb 27 2003

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 113, Example (2), D(n; 1,2,4,10).

Crossrefs

First differences are in A000115.

Programs

  • Maple
    a:= proc(n) local m, r; m:= iquo(n, 10, 'r'); r:= r+1; (53+ (135+ 100*m) *m) *m/6+ [1, 2, 4, 6, 9, 13, 18, 24, 31, 39][r]+ [0, 5, 11, 18, 26, 35, 45, 56, 68, 81][r]*m+ (r-1)*5 *m^2 end: seq(a(n), n=0..100); # Alois P. Heinz, Oct 05 2008
  • Mathematica
    CoefficientList[Series[1/((1-x)^2*(1-x^2)*(1-x^5)),{x,0,50}],x] (* Vincenzo Librandi, Feb 24 2012 *)
    LinearRecurrence[{2,0,-2,1,1,-2,0,2,-1},{1,2,4,6,9,13,18,24,31},60] (* Harvey P. Dale, Oct 03 2018 *)
  • PARI
    a(n)=floor((n+8)*(2*n^2+11*n+18)/120) \\ Tani Akinari, May 14 2014

Formula

G.f.: 1/((1-x)^2*(1-x^2)*(1-x^5)) = 1 / ((1+x)*(x^4+x^3+x^2+x+1)*(x-1)^4).
a(n) = floor((n+8)*(2*n^2+11*n+18)/120). - Tani Akinari, May 14 2014

A246720 Number A(n,k) of partitions of n into parts of the k-th list of distinct parts in the order given by A246688; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 2, 0, 1, 0, 1, 1, 0, 2, 1, 1, 0, 1, 0, 1, 1, 3, 0, 1, 0, 1, 1, 0, 2, 0, 3, 1, 1, 0, 1, 0, 1, 0, 2, 0, 4, 0, 1, 0, 1, 0, 1, 1, 1, 2, 1, 4, 1, 1, 0, 1, 1, 0, 1, 2, 0, 3, 0, 5, 0, 1, 0, 1, 1, 2, 0, 1, 2, 0, 3, 0, 5, 1, 1, 0
Offset: 0

Author

Alois P. Heinz, Sep 02 2014

Keywords

Comments

The first lists of distinct parts in the order given by A246688 are: 0:[], 1:[1], 2:[2], 3:[1,2], 4:[3], 5:[1,3], 6:[4], 7:[1,4], 8:[2,3], 9:[5], 10:[1,2,3], 11:[1,5], 12:[2,4], 13:[6], 14:[1,2,4], 15:[1,6], 16:[2,5], 17:[3,4], 18:[7], 19:[1,2,5], 20:[1,3,4], ... .

Examples

			Square array A(n,k) begins:
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1,  1, ...
  0, 1, 0, 1, 0, 1, 0, 1, 0, 0,  1, 1, 0, 0,  1, ...
  0, 1, 1, 2, 0, 1, 0, 1, 1, 0,  2, 1, 1, 0,  2, ...
  0, 1, 0, 2, 1, 2, 0, 1, 1, 0,  3, 1, 0, 0,  2, ...
  0, 1, 1, 3, 0, 2, 1, 2, 1, 0,  4, 1, 2, 0,  4, ...
  0, 1, 0, 3, 0, 2, 0, 2, 1, 1,  5, 2, 0, 0,  4, ...
  0, 1, 1, 4, 1, 3, 0, 2, 2, 0,  7, 2, 2, 1,  6, ...
  0, 1, 0, 4, 0, 3, 0, 2, 1, 0,  8, 2, 0, 0,  6, ...
  0, 1, 1, 5, 0, 3, 1, 3, 2, 0, 10, 2, 3, 0,  9, ...
  0, 1, 0, 5, 1, 4, 0, 3, 2, 0, 12, 2, 0, 0,  9, ...
  0, 1, 1, 6, 0, 4, 0, 3, 2, 1, 14, 3, 3, 0, 12, ...
		

Crossrefs

Main diagonal gives A246721.
Cf. A246688, A246690 (the same for compositions).

Programs

  • Maple
    b:= proc(n, i) b(n, i):= `if`(n=0, [[]], `if`(i>n, [],
          [map(x->[i, x[]], b(n-i, i+1))[], b(n, i+1)[]]))
        end:
    f:= proc() local i, l; i, l:=0, [];
          proc(n) while n>=nops(l)
            do l:=[l[], b(i, 1)[]]; i:=i+1 od; l[n+1]
          end
        end():
    g:= proc(n, l) option remember; `if`(n=0, 1, `if`(l=[], 0,
          add(g(n-l[-1]*j, subsop(-1=NULL, l)), j=0..n/l[-1])))
        end:
    A:= (n, k)-> g(n, f(k)):
    seq(seq(A(n, d-n), n=0..d), d=0..16);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, {{}}, If[i > n, {}, Join[Prepend[#, i]& /@ b[n - i, i + 1], b[n, i + 1]]]];
    f = Module[{i = 0, l = {}}, Function[n, While[ n >= Length[l], l = Join[l, b[i, 1]]; i++ ]; l[[n + 1]]]];
    g[n_, l_] := g[n, l] = If[n == 0, 1, If[l == {}, 0, Sum[g[n - l[[-1]] j, ReplacePart[l, -1 -> Nothing]], {j, 0, n/l[[-1]]}]]];
    A[n_, k_] := g[n, f[k]];
    Table[Table[A[n, d - n], {n, 0, d}], {d, 0, 16}] // Flatten (* Jean-François Alcover, Dec 07 2020, after Alois P. Heinz *)

A025802 Expansion of 1/((1-x^2)*(1-x^4)*(1-x^5)).

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 2, 1, 3, 2, 4, 2, 5, 3, 6, 4, 7, 5, 8, 6, 10, 7, 11, 8, 13, 10, 14, 11, 16, 13, 18, 14, 20, 16, 22, 18, 24, 20, 26, 22, 29, 24, 31, 26, 34, 29, 36, 31, 39, 34, 42, 36, 45, 39, 48, 42, 51, 45, 54, 48, 58, 51
Offset: 0

Keywords

Comments

a(n) is the number of partitions of n into parts 2, 4, and 5. - Hoang Xuan Thanh, Jun 18 2025

Crossrefs

Cf. A000115.

Programs

  • Mathematica
    CoefficientList[Series[1/((1-x^2)(1-x^4)(1-x^5)),{x,0,70}],x] (* Harvey P. Dale, Sep 15 2011 *)

Formula

From R. J. Mathar, Jun 23 2021: (Start)
a(n)-a(n-2) = A165190(n).
a(n)-a(n-4) = A008616(n). (End)
a(n) = floor((n^2 + n*(11+5*(-1)^n) + 53 + 27*(-1)^n)/80). - Hoang Xuan Thanh, Jun 18 2025
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