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 1-10 of 37 results. Next

A107244 Sum of squares of hexanacci numbers (A001592, Fibonacci 6-step numbers).

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 2, 6, 22, 86, 342, 1366, 5335, 20960, 82464, 324528, 1277104, 5025200, 19770800, 77789489, 306071370, 1204272270, 4738336974, 18643463374, 73354544590, 288620849614, 1135607911375, 4468164041216, 17580442344960
Offset: 0

Views

Author

Jonathan Vos Post, May 19 2005

Keywords

Comments

Primes include: a(6) = 2. Semiprimes include a(7) = 6 = 2 * 3, a(8) = 22 = 2 * 11, a(9) = 86 = 2 * 43, a(11) = 1366 = 2 * 683, a(19) = 77789489 = 3989 * 19501, a(23) = 18643463374 = 2 * 9321731687,

Examples

			a(0) = 0 = 0^2
a(1) = 0 = 0^2 + 0^2
a(2) = 0 = 0^2 + 0^2 + 0^2
a(3) = 0 = 0^2 + 0^2 + 0^2 + 0^2
a(4) = 0 = 0^2 + 0^2 + 0^2 + 0^2 + 0^2
a(5) = 1 = 0^2 + 0^2 + 0^2 + 0^2 + 0^2 + 1^2
a(6) = 2 = 0^2 + 0^2 + 0^2 + 0^2 + 0^2 + 1^2 + 1^2
a(7) = 6 = 0^2 + 0^2 + 0^2 + 0^2 + 0^2 + 1^2 + 1^2 + 2^2
a(8) = 22 = 0^2 + 0^2 +0^2 + 0^2 + 0^2 + 1^2 + 1^2 + 2^2 + 4^2
		

Crossrefs

Programs

  • Mathematica
    Accumulate[LinearRecurrence[{1,1,1,1,1,1},{0,0,0,0,0,1},50]^2] (* Harvey P. Dale, Jan 19 2012 *)
    LinearRecurrence[{3, 2, 4, 6, 14, 28, -67, -9, -8, 28, -8, -12, 20, 5, 5, -10, 0, 2, -2, 0, -1, 1},{0, 0, 0, 0, 0, 1, 2, 6, 22, 86, 342, 1366, 5335, 20960, 82464, 324528, 1277104, 5025200, 19770800, 77789489, 306071370, 1204272270},29] (* Ray Chandler, Aug 02 2015 *)

Formula

a(n) = F_6(0)^2 + F_6(1)^2 + ... F_6(n)^2, where F_6(n) = A001592(n). a(0) = 0, a(n+1) = a(n) + A001592(n).
a(n)= 3*a(n-1) +2*a(n-2) +4*a(n-3) +6*a(n-4) +14*a(n-5) +28*a(n-6) -67*a(n-7) -9*a(n-8) -8*a(n-9) +28*a(n-10) -8*a(n-11) -12*a(n-12) +20*a(n-13) +5*a(n-14) +5*a(n-15) -10*a(n-16) +2*a(n-18) -2*a(n-19) -a(n-21) +a(n-22). [From R. J. Mathar, Aug 11 2009]

A104413 Number of prime factors, with multiplicity, of the hexanacci numbers A001592.

Original entry on oeis.org

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

Views

Author

Jonathan Vos Post, Mar 06 2005

Keywords

Crossrefs

Programs

  • Mathematica
    PrimeOmega[LinearRecurrence[{1, 1, 1, 1, 1, 1}, {1, 1, 2, 4, 8, 16}, 100]] (* Amiram Eldar, May 16 2021 *)

Formula

a(n) = A001222(A001592(n)).

Extensions

Offset changed to 5 by Georg Fischer, Dec 19 2020
More terms from Joerg Arndt, Dec 19 2020

A105758 Indices of prime hexanacci (or Fibonacci 6-step) numbers A001592 (using offset -4).

Original entry on oeis.org

3, 36, 37, 92, 660, 6091, 8415, 11467, 13686, 38831, 49828, 97148
Offset: 1

Views

Author

T. D. Noe, Apr 22 2005

Keywords

Comments

No other n < 30000.
This sequence uses the convention of the Noe and Post reference. Their indexing scheme differs by 4 from the indices in A001592. Sequence A249635 lists the indices of the same primes (A105759) using the indexing scheme as defined in A001592. - Robert Price, Nov 02 2014 [Edited by M. F. Hasler, Apr 22 2018]
a(13) > 3*10^5. - Robert Price, Nov 02 2014

Crossrefs

Cf. A105759 (prime Fibonacci 6-step numbers), A249635 (= a(n) + 4), A001592.
Cf. A000045, A000073, A000078 (and A001631), A001591, A122189 (or A066178), A079262, A104144, A122265, A168082, A168083 (Fibonacci, tribonacci, tetranacci numbers and other generalizations).
Cf. A005478, A092836, A104535, A105757, A105761, ... (primes in these sequence).
Cf. A001605, A303263, A303264 (and A104534 and A247027), A248757 (and A105756), ... (indices of primes in A000045, A000073, A000078, ...).

Programs

  • Mathematica
    a={1, 0, 0, 0, 0, 0}; lst={}; Do[s=Plus@@a; a=RotateLeft[a]; a[[ -1]]=s; If[PrimeQ[s], AppendTo[lst, n]], {n, 30000}]; lst

Formula

a(n) = A249635(n) - 4. A105759(n) = A001592(A249635(n)) = A001592(a(n) + 4). - M. F. Hasler, Apr 22 2018

Extensions

a(10)-a(12) from Robert Price, Nov 02 2014
Edited by M. F. Hasler, Apr 22 2018

A105759 Prime Fibonacci 6-step numbers, A001592.

Original entry on oeis.org

2, 13435170943, 26649774581, 610186256014622144673892607
Offset: 1

Views

Author

T. D. Noe, Apr 22 2005

Keywords

Comments

The next term has 196 digits. - Harvey P. Dale, Apr 23 2025

Crossrefs

Cf. A105758 (indices of prime Fibonacci 6-step numbers).

Programs

  • Mathematica
    a={1, 0, 0, 0, 0, 0}; lst={}; Do[s=Plus@@a; a=RotateLeft[a]; a[[ -1]]=s; If[PrimeQ[s], AppendTo[lst, s]], {n, 1000}]; lst
    Select[LinearRecurrence[{1,1,1,1,1,1},{1,0,0,0,0,0},100],PrimeQ] (* Harvey P. Dale, Apr 23 2025 *)

A249635 Indices of prime Fibonacci 6-step numbers, A001592.

Original entry on oeis.org

7, 40, 41, 96, 664, 6095, 8419, 11471, 13690, 38835, 49832, 97152
Offset: 1

Views

Author

Robert Price, Nov 02 2014

Keywords

Comments

This sequence is similar to A105758 but uses the indexing scheme defined by A001592, whose indices start with 0.
a(13) > 3*10^5.

Crossrefs

Programs

  • Mathematica
    a = {0, 0, 0, 0, 0, 1}; For[n = 6, n ≤ 1000, n++, sum = Plus @@ a;
    If[PrimeQ[sum], Print[n]]; a = RotateLeft[a]; a[[6]] = sum]

Formula

a(n) = A105758 (n) + 4.

A381508 Pisano period of Hexanacci numbers (A001592) mod n.

Original entry on oeis.org

1, 7, 728, 14, 208, 728, 342, 28, 2184, 1456, 354312, 728, 9520, 2394, 1456, 56, 709928, 2184, 5227320, 1456, 124488, 354312, 279840, 728, 1040, 9520, 6552, 2394, 243880, 1456, 71040, 112, 4606056, 4969496, 35568, 2184, 20362908, 5227320, 123760, 1456, 201840
Offset: 1

Views

Author

Martin Guerra and Doron Zeilberger, Apr 24 2025

Keywords

Crossrefs

Programs

  • Maple
    # load programs from linked file:
    seq(Pis([[0$5, 1],[1$6]],n,400000), n=1..16);
  • Python
    from math import lcm
    from functools import lru_cache
    from sympy import factorint
    @lru_cache(maxsize=None)
    def A381508(n):
        if n == 1:
            return 1
        f = factorint(n).items()
        if len(f) > 1:
            return lcm(*(A381508(a**b) for a,b in f))
        else:
            k, x = 1, (0,0,0,0,1,1)
            while x != (0,0,0,0,0,1):
                k += 1
                x = x[1:]+(sum(x) % n,)
            return k # Chai Wah Wu, Apr 25 2025

Extensions

a(17)-a(41) from Alois P. Heinz, Apr 25 2025

A000383 Hexanacci numbers with a(0) = ... = a(5) = 1.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 6, 11, 21, 41, 81, 161, 321, 636, 1261, 2501, 4961, 9841, 19521, 38721, 76806, 152351, 302201, 599441, 1189041, 2358561, 4678401, 9279996, 18407641, 36513081, 72426721, 143664401, 284970241, 565262081, 1121244166, 2224080691, 4411648301
Offset: 0

Views

Author

Keywords

References

  • 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

Cf. A060455.
Cf. A001592 (Hexanacci numbers with a(0) = ... = a(4) = 0 and a(5)=1).
Cf. A247192 (indices of primes in this sequence).
Cf. A249413 (primes in this sequence).

Programs

  • Maple
    A000383:=(-1+z**2+2*z**3+3*z**4+4*z**5)/(-1+z**2+z**3+z**4+z**5+z+z**6); # Simon Plouffe in his 1992 dissertation
    a:= n-> (Matrix([[1$6]]). Matrix(6, (i,j)-> if (i=j-1) or j=1 then 1 else 0 fi)^n)[1,6]: seq(a(n), n=0..28); # Alois P. Heinz, Aug 26 2008
  • Mathematica
    LinearRecurrence[{1,1,1,1,1,1},{1,1,1,1,1,1},50] (* Harvey P. Dale, Oct 30 2013 *)
  • PARI
    a(n)=([0,1,0,0,0,0; 0,0,1,0,0,0; 0,0,0,1,0,0; 0,0,0,0,1,0; 0,0,0,0,0,1; 1,1,1,1,1,1]^n*[1;1;1;1;1;1])[1,1] \\ Charles R Greathouse IV, Sep 24 2015

Formula

G.f. ( -1+x^2+2*x^3+3*x^4+4*x^5 ) / ( -1+x+x^2+x^3+x^4+x^5+x^6 ). - R. J. Mathar, Oct 11 2011

A079262 Octanacci numbers: a(0)=a(1)=...=a(6)=0, a(7)=1; for n >= 8, a(n) = Sum_{i=1..8} a(n-i).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 4, 8, 16, 32, 64, 128, 255, 509, 1016, 2028, 4048, 8080, 16128, 32192, 64256, 128257, 256005, 510994, 1019960, 2035872, 4063664, 8111200, 16190208, 32316160, 64504063, 128752121, 256993248, 512966536, 1023897200, 2043730736
Offset: 0

Views

Author

Michael Joseph Halm, Feb 04 2003

Keywords

Comments

a(n+7) is the number of compositions of n into parts <= 8. - Joerg Arndt, Sep 24 2020

Examples

			a(16) = 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.
		

Crossrefs

Row 8 of arrays A048887 and A092921 (k-generalized Fibonacci numbers).
Cf. A253706, A253705. Primes and indices of primes in this sequence.

Programs

  • Maple
    for j from 0 to 6 do a[j]:=0 od: a[7]:=1: for n from 8 to 45 do a[n]:=sum(a[n-i],i=1..8) od:seq(a[n],n=0..45); # Emeric Deutsch, Apr 16 2005
  • Mathematica
    LinearRecurrence[{1, 1, 1, 1, 1, 1, 1, 1}, {0, 0, 0, 0, 0, 0, 0, 1}, 50] (* Vladimir Joseph Stephan Orlovsky, May 25 2011 *)
    With[{nn=8},LinearRecurrence[Table[1,{nn}],Join[Table[0,{nn-1}],{1}],50]] (* Harvey P. Dale, Aug 17 2013 *)

Formula

G.f.: x^7/(1 - x - x^2 - x^3 - x^4 - x^5 - x^6 - x^7 - x^8). - Emeric Deutsch, Apr 16 2005
a(1)..a(9) = 1, 1, 2, 4, 8, 16, 32, 64, 128. a(10) and following are given by 63*2^(n-8)+(1/2+sqrt(5/4))^(n-6)/sqrt(5)-(1/2-sqrt(5/4))^(n-6)/sqrt(5). Offset 10. a(10)=255. - Al Hakanson (hawkuu(AT)gmail.com), Feb 14 2009
Another form of the g.f.: f(z) = (z^7 - z^8)/(1 - 2*z + z^9), then a(n) = Sum_{i=0..floor((n-7)/9)} (-1)^i*binomial(n-7-8*i,i)*2^(n-7-9*i) - Sum_{i=0..floor((n-8)/9)} (-1)^i*binomial(n-8-8*i,i)*2^(n-8-9*i) with Sum_{i=m..n} alpha(i) = 0 for m>n. - Richard Choulet, Feb 22 2010
Sum_{k=0..7*n} a(k+b)*A171890(n,k) = a(8*n+b), b>=0.
a(n) = 2*a(n-1) - a(n-9). - Vincenzo Librandi, Dec 20 2010

Extensions

Corrected by Joao B. Oliveira (oliveira(AT)inf.pucrs.br), Nov 25 2004

A066178 Number of binary bit strings of length n with no block of 8 or more 0's. Nonzero heptanacci numbers, A122189.

Original entry on oeis.org

1, 1, 2, 4, 8, 16, 32, 64, 127, 253, 504, 1004, 2000, 3984, 7936, 15808, 31489, 62725, 124946, 248888, 495776, 987568, 1967200, 3918592, 7805695, 15548665, 30972384, 61695880, 122895984, 244804400, 487641600
Offset: 0

Views

Author

Len Smiley, Dec 14 2001

Keywords

Comments

Analogous bit string description and o.g.f. (1-x)/(1-2x+x^{k+1}) works for nonzero k-nacci numbers.
Compositions of n into parts <= 7. - Joerg Arndt, Aug 06 2012

Crossrefs

Cf. A000045 (k=2, Fibonacci numbers), A000073 (k=3, tribonacci) A000078 (k=4, tetranacci) A001591 (k=5, pentanacci) A001592 (k=6, hexanacci), A122189 (k=7, heptanacci).
Row 7 of arrays A048887 and A092921 (k-generalized Fibonacci numbers).

Programs

  • Mathematica
    a[0] = a[1] = 1; a[2] = 2; a[3] = 4; a[4] = 8; a[5] = 16; a[6] = 32; a[7] = 64; a[n_] := 2*a[n - 1] - a[n - 8]; Array[a, 31, 0]
    CoefficientList[ Series[(1 - x)/(1 - 2 x + x^8), {x, 0, 30}], x]
    LinearRecurrence[{1,1,1,1,1,1,1},{1,1,2,4,8,16,32},40] (* Harvey P. Dale, Nov 16 2014 *)

Formula

O.g.f.: 1/(1 - x - x^2 - x^3 - x^4 - x^5 - x^6 - x^7).
a(n) = Sum_{i=n-7..n-1} a(i).
a(n) = round((r-1)/((t+1)*r - 2*t) * r^(n-1)), where r is the heptanacci constant, the real root of the equation x^(t+1) - 2*x^t + 1 = 0 which is greater than 1. The formula could also be used for a k-step Fibonacci sequence if r is replaced by the k-bonacci constant, as in A000045, A000073, A000078, A001591, A001592. - Zhao Hui Du, Aug 24 2008
a(n) = 2*a(n-1) - a(n-8). - Vincenzo Librandi, Dec 20 2010

Extensions

Definition corrected by Vincenzo Librandi, Dec 20 2010

A092921 Array F(k, n) read by descending antidiagonals: k-generalized Fibonacci numbers in row k >= 1, starting (0, 1, 1, ...), for column n >= 0.

Original entry on oeis.org

0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 2, 1, 1, 0, 1, 3, 2, 1, 1, 0, 1, 5, 4, 2, 1, 1, 0, 1, 8, 7, 4, 2, 1, 1, 0, 1, 13, 13, 8, 4, 2, 1, 1, 0, 1, 21, 24, 15, 8, 4, 2, 1, 1, 0, 1, 34, 44, 29, 16, 8, 4, 2, 1, 1, 0, 1, 55, 81, 56, 31, 16, 8, 4, 2, 1, 1, 0, 1, 89, 149, 108, 61, 32, 16, 8, 4, 2, 1, 1, 0
Offset: 0

Views

Author

Ralf Stephan, Apr 17 2004

Keywords

Comments

For all k >= 1, the k-generalized Fibonacci number F(k,n) satisfies the recurrence obtained by adding more terms to the recurrence of the Fibonacci numbers.
The number of tilings of an 1 X n rectangle with tiles of size 1 X 1, 1 X 2, ..., 1 X k is F(k,n).
T(k,n) is the number of 0-balanced ordered trees with n edges and height k (height is the number of edges from root to a leaf). - Emeric Deutsch, Jan 19 2007
Brlek et al. (2006) call this table "number of psp-polyominoes with flat bottom". - N. J. A. Sloane, Oct 30 2018

Examples

			From _Peter Luschny_, Apr 03 2021: (Start)
Array begins:
                n = 0  1  2  3  4  5   6   7   8    9   10
  -------------------------------------------------------------
  [k=1, mononacci ] 0, 1, 1, 1, 1, 1,  1,  1,  1,   1,   1, ...
  [k=2, Fibonacci ] 0, 1, 1, 2, 3, 5,  8, 13, 21,  34,  55, ...
  [k=3, tribonacci] 0, 1, 1, 2, 4, 7, 13, 24, 44,  81, 149, ...
  [k=4, tetranacci] 0, 1, 1, 2, 4, 8, 15, 29, 56, 108, 208, ...
  [k=5, pentanacci] 0, 1, 1, 2, 4, 8, 16, 31, 61, 120, 236, ...
  [k=6]             0, 1, 1, 2, 4, 8, 16, 32, 63, 125, 248, ...
  [k=7]             0, 1, 1, 2, 4, 8, 16, 32, 64, 127, 253, ...
  [k=8]             0, 1, 1, 2, 4, 8, 16, 32, 64, 128, 255, ...
  [k=9]             0, 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, ...
Note that the first parameter in F(k, n) refers to rows, and the second parameter refers to columns. This is always the case. Only the usual naming convention for the indices is not adhered to because it is common to call the row sequences k-bonacci numbers. (End)
.
From _Peter Luschny_, Aug 12 2015: (Start)
As a triangle counting compositions of n with largest part k:
  [n\k]| [0][1] [2] [3] [4][5][6][7][8][9]
   [0] | [0]
   [1] | [0, 1]
   [2] | [0, 1,  1]
   [3] | [0, 1,  1,  1]
   [4] | [0, 1,  2,  1,  1]
   [5] | [0, 1,  3,  2,  1, 1]
   [6] | [0, 1,  5,  4,  2, 1, 1]
   [7] | [0, 1,  8,  7,  4, 2, 1, 1]
   [8] | [0, 1, 13, 13,  8, 4, 2, 1, 1]
   [9] | [0, 1, 21, 24, 15, 8, 4, 2, 1, 1]
For example for n=7 and k=3 we have the 7 compositions [3, 3, 1], [3, 2, 2], [3, 2, 1, 1], [3, 1, 3], [3, 1, 2, 1], [3, 1, 1, 2], [3, 1, 1, 1, 1]. (End)
		

Crossrefs

Columns converge to A166444: each column n converges to A166444(n) = 2^(n-2).
Rows 1-8 are (shifted) A057427, A000045, A000073, A000078, A001591, A001592, A066178, A079262.
Essentially a reflected version of A048887.
See A048004 and A126198 for closely related arrays.
Cf. A066099.

Programs

  • Maple
    F:= proc(k, n) option remember; `if`(n<2, n,
          add(F(k, n-j), j=1..min(k,n)))
        end:
    seq(seq(F(k, d+1-k), k=1..d+1), d=0..12);  # Alois P. Heinz, Nov 02 2016
    # Based on the above function:
    Arow := (k, len) -> seq(F(k, j), j = 0..len):
    seq(lprint(Arow(k, 14)), k = 1..10); # Peter Luschny, Apr 03 2021
  • Mathematica
    F[k_, n_] := F[k, n] = If[n<2, n, Sum[F[k, n-j], {j, 1, Min[k, n]}]];
    Table[F[k, d+1-k], {d, 0, 12}, {k, 1, d+1}] // Flatten (* Jean-François Alcover, Jan 11 2017, translated from Maple *)
  • PARI
    F(k,n)=if(n<2,if(n<1,0,1),sum(i=1,k,F(k,n-i)))
    
  • PARI
    T(m,n)=!!n*(matrix(m,m,i,j,j==i+1||i==m)^(n+m-2))[1,m] \\ M. F. Hasler, Apr 20 2018
    
  • PARI
    F(k,n) = if(n==0,0, polcoeff(lift(Mod('x, Pol(vector(k+1,i, if(i==1,1,-1))))^(n+k-2)), k-1)); \\ Kevin Ryde, Jun 05 2020
    
  • Sage
    # As a triangle of compositions of n with largest part k.
    C = lambda n,k: Compositions(n, max_part=k, inner=[k]).cardinality()
    for n in (0..9): [C(n,k) for k in (0..n)] # Peter Luschny, Aug 12 2015

Formula

F(k,n) = F(k,n-1) + F(k,n-2) + ... + F(k,n-k); F(k,1) = 1 and F(k,n) = 0 for n <= 0.
G.f.: x/(1-Sum_{i=1..k} x^i).
F(k,n) = 2^(n-2) for 1 < n <= k+1. - M. F. Hasler, Apr 20 2018
F(k,n) = Sum_{j=0..floor(n/(k+1))} (-1)^j*((n - j*k) + j + delta(n,0))/(2*(n - j*k) + delta(n,0))*binomial(n - j*k, j)*2^(n-j*(k+1)), where delta denotes the Kronecker delta (see Corollary 3.2 in Parks and Wills). - Stefano Spezia, Aug 06 2022
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