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 11 results. Next

A131295 a(n)=ds_4(a(n-1))+ds_4(a(n-2)), a(0)=0, a(1)=1; where ds_4=digital sum base 4.

Original entry on oeis.org

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

Views

Author

Hieronymus Fischer, Jun 27 2007

Keywords

Comments

The digital sum analog (in base 4) of the Fibonacci recurrence.
When starting from index n=3, periodic with Pisano period A001175(3)=8.
Also a(n)==A004090(n) modulo 3 (A004090(n)=digital sum of Fib(n)).
For general bases p>2, the inequality 2<=a(n)<=2p-3 holds for n>2. Actually, a(n)<=5=A131319(4) for the base p=4.
a(n) and Fib(n)=A000045(n) are congruent modulo 3 which implies that (a(n) mod 3) is equal to (Fib(n) mod 3)=A082115(n-1) (for n>0). Thus (a(n) mod 3) is periodic with the Pisano period = A001175(3)=8 too. - Hieronymus Fischer

Examples

			a(8)=3, since a(6)=5=11(base 4), ds_4(5)=2,
a(7)=4=10(base 4), ds_4(4)=1 and so a(8)=2+1.
		

Crossrefs

Programs

  • Mathematica
    nxt[{a_,b_}]:={b,Total[IntegerDigits[a,4]]+Total[IntegerDigits[b,4]]}; NestList[ nxt,{0,1},110][[All,1]] (* Harvey P. Dale, Jul 30 2018 *)

Formula

a(n)=a(n-1)+a(n-2)-3*(floor(a(n-1)/4)+floor(a(n-2)/4)).
a(n)=floor(a(n-1)/4)+floor(a(n-2)/4)+(a(n-1)mod 4)+(a(n-2)mod 4).
a(n)=A002265(a(n-1))+A002265(a(n-2))+A010873(a(n-1))+A010873(a(n-2)).
a(n)=Fib(n)-3*sum{1A000045(n).

A082116 Fibonacci sequence (mod 5).

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Apr 03 2003

Keywords

Comments

This sequence contains the complete set of residues modulo 5. See A079002. - Michel Marcus, Jan 31 2020

References

  • S. Vajda, Fibonacci and Lucas numbers and the Golden Section, Ellis Horwood Ltd., Chichester, 1989. See p. 88. - N. J. A. Sloane, Feb 20 2013

Crossrefs

Programs

Formula

Sequence is periodic with Pisano period 20.
a(n) = 2 + ((n mod 20) - ((n - 1) mod 20) - ((n - 3) mod 20) - ((n - 4) mod 20) + 3*((n - 5) mod 20) - 3*((n - 6) mod 20) + 2*((n - 8) mod 20) - 3*((n - 9) mod 20) + 4*((n - 10) mod 20) - 4*((n - 11) mod 20) + ((n - 13) mod 20) + ((n - 14) mod 20) + 2*((n - 15) mod 20) - 2*((n - 16) mod 20) - 2*((n - 18) mod 20) + 3*((n - 19) mod 20))/20. - Hieronymus Fischer, Jun 30 2007
G.f.: (x + x^2 + 2x^3 + 3x^4 + 3x^6 + 3x^7 + x^8 + 4x^9 + 4x^11 + 4x^12 + 3x^13 + 2x^14 + 2x^16 + 2x^17 + 4x^18 + x^19)/(1 - x^20), not reduced. - Hieronymus Fischer, Jun 30 2007
a(n) = A010073(n) mod 5. - Hieronymus Fischer, Jun 30 2007
G.f.: -x*(1 + x + x^2 + 2*x^3 + 3*x^6 - x^7 - 2*x^8 - x^4 + x^9 + 4*x^10 + x^11) / ( (x - 1) * (x^4 + x^3 + x^2 + x + 1) * (x^8 - x^6 + x^4 - x^2 + 1) ). - R. J. Mathar, Jul 14 2012

Extensions

Added a(0)=0 from Vincenzo Librandi, Feb 04 2014

A079344 F(n) mod 8, where F(n) = A000045(n) is the n-th Fibonacci number.

Original entry on oeis.org

0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5
Offset: 0

Views

Author

Jon Perry, Jan 04 2003

Keywords

Comments

This sequence does not contain the complete set of residues modulo 8. See A079002. - Michel Marcus, Jan 31 2020

Examples

			a(8) = F(8) mod 8 = 21 mod 8 = 5.
		

Crossrefs

Programs

  • Magma
    [Fibonacci(n) mod 8: n in [0..100]]; // Vincenzo Librandi, Feb 04 2014
  • Mathematica
    Mod[Fibonacci[Range[0,110]],8] (* or *) LinearRecurrence[ {1,0,0,-1,1,0,0,-1,1},{0,1,1,2,3,5,0,5,5},110] (* Harvey P. Dale, Jan 16 2014 *)
  • PARI
    for (n=0,100,print1(fibonacci(n)%8","))
    

Formula

Sequence is periodic with Pisano period 12 = A001175(8).
G.f.: -x*(1+x^2+x^3+3*x^4+6*x^6-5*x^5+x^7) / ( (x-1)*(x^2-x+1)*(1+x+x^2)*(x^4-x^2+1) ). - R. J. Mathar, Aug 08 2012

Extensions

Edited by N. J. A. Sloane, Dec 06 2008 at the suggestion of R. J. Mathar

A082117 Fibonacci sequence (mod 6).

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Apr 03 2003

Keywords

Crossrefs

Programs

Formula

Sequence is periodic with Pisano period 24 = A001175(6).
G.f.: -x*(x^22 + 5*x^21 + 2*x^20 + 3*x^19 + 5*x^18 + 4*x^17 + x^16 + 3*x^15 + 4*x^14 + 5*x^13 + 5*x^12 + 5*x^10 + x^9 + 4*x^8 + 3*x^7 + x^6 + 2*x^5 + 5*x^4 + 3*x^3 + 2*x^2 + x + 1)/((x - 1)*(x + 1)*(x^2 - x + 1)*(x^2 + 1)*(x^2 + x + 1)*(x^4 - x^2 + 1)*(x^4 + 1)*(x^8 - x^4 + 1)). - Colin Barker, Aug 15 2012

Extensions

Added a(0)=0 from Vincenzo Librandi, Feb 04 2014

A280154 a(n) = 5*Lucas(n).

Original entry on oeis.org

10, 5, 15, 20, 35, 55, 90, 145, 235, 380, 615, 995, 1610, 2605, 4215, 6820, 11035, 17855, 28890, 46745, 75635, 122380, 198015, 320395, 518410, 838805, 1357215, 2196020, 3553235, 5749255, 9302490, 15051745, 24354235, 39405980, 63760215, 103166195, 166926410, 270092605, 437019015
Offset: 0

Views

Author

Bruno Berselli, Dec 27 2016

Keywords

Comments

Fibonacci sequence beginning 10, 5.
After 5, the sequence provides the 3rd column of the rectangular array in A213590.
After 5, all terms belong to A191921 because a(n) = Lucas(n+4) - 3*Lucas(n-1).
From G. C. Greubel, Dec 27 2016: (Start)
{a(n) mod 3} yields (1,2,0,2,2,1,0,1), repeated, and is given as A082115.
{a(n) mod 6} yields (4,5,3,2,5,1,0,1,1,2,3,5,2,1,3,4,1,5,0,5,5,4,3,1) and is given as A082117. (End)

Crossrefs

Subsequence of A084176.
Cf. A022088: 5*Fibonacci(n).
Cf. A022359: Lucas(n+5) + Lucas(n-5).
Cf. sequences with formula Fibonacci(n+k) + Fibonacci(n-k): A006355 (k=0, without the initial 1), A000032 (k=1), A022086 (k=2), A022112 (k=3, with an initial 4), A022090 (k=4), this sequence (k=5), A022352 (k=6).

Programs

  • Magma
    [5*Lucas(n): n in [0..40]];
    
  • Maple
    F := n -> combinat:-fibonacci(n):
    seq(F(n+5) + F(n-5), n=0..38); # Peter Luschny, Dec 29 2016
  • Mathematica
    Table[5 LucasL[n], {n, 0, 40}]
  • PARI
    vector(40, n, n--; fibonacci(n+5)+fibonacci(n-5))
    
  • Sage
    def A280154():
        x, y = 10, 5
        while True:
            yield x
            x, y = y, x + y
    a = A280154(); print([next(a) for  in range(39)]) # _Peter Luschny, Dec 29 2016

Formula

G.f.: 5*(2 - x)/(1 - x - x^2).
a(n) = a(n-1) + a(n-2) for n>1.
a(n) = Fibonacci(n+5) + Fibonacci(n-5), with Fibonacci(-k) = -(-1)^k*Fibonacci(k) for the negative indices.

A004696 a(n) = floor(Fibonacci(n)/3).

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 2, 4, 7, 11, 18, 29, 48, 77, 125, 203, 329, 532, 861, 1393, 2255, 3648, 5903, 9552, 15456, 25008, 40464, 65472, 105937, 171409, 277346, 448756, 726103, 1174859, 1900962, 3075821, 4976784, 8052605, 13029389, 21081995, 34111385, 55193380
Offset: 0

Views

Author

Keywords

Examples

			G.f. = x^4 + x^5 + 2*x^6 + 4*x^7 + 7*x^8 + 11*x^9 + 18*x^10 + 29*x^11 + 48*x^12 + ...
		

Crossrefs

Cf. A000045 (Fibonacci(n)).
Cf. A082115 (Fibonacci(n) (mod 3)).
Cf. A293543 (ceiling(Fibonacci(n)/3)).
Cf. A293544 (round(Fibonacci(n)/3)).

Programs

  • Magma
    [Floor(Fibonacci(n)/3): n in [0..40]]; // Vincenzo Librandi, Jul 09 2012
    
  • Maple
    seq(iquo(fibonacci(n),3),n=0..40); # Zerinvary Lajos, Apr 20 2008
  • Mathematica
    CoefficientList[Series[x^4 (x^4 + x^3 + 1)/((1 - x^8) (1 -x - x^2)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 09 2012 *)
    Floor[Fibonacci[Range[0, 40]]/3] (* G. C. Greubel, May 22 2019 *)
    Table[Floor[Fibonacci[n]/3], {n, 0, 20}] (* Eric W. Weisstein, Feb 09 2025 *)
    Table[(8 Fibonacci[n] + 3 (-1)^n - 9 + Cos[Pi n/2] (6 - 4 Sin[Pi n/4]) + 4 Sqrt[2] Sin[Pi n/4] Sin[Pi n/2])/24, {n, 0, 20}] (* Eric W. Weisstein, Feb 09 2025 *)
  • PARI
    vector(40, n, n--; fibonacci(n)\3) \\ Altug Alkan, Nov 06 2015
    
  • PARI
    concat(vector(4), Vec(x^4*(x^4+x^3+1)/((1-x^8)*(1-x-x^2)) + O(x^40))) \\ Altug Alkan, Nov 06 2015
    
  • Sage
    [floor(fibonacci(n)/3) for n in (0..40)] # G. C. Greubel, May 22 2019

Formula

G.f.: x^4*(1 +x^3 +x^4) / ((1-x^8)*(1-x-x^2)).
a(n) = (A000045(n) - A082115(n))/3. - R. J. Mathar, Jul 14 2012
From Vladimir Reshetnikov, Nov 05 2015: (Start)
a(n) = (8*A000045(n) + 3*(-1)^n - 9 + cos(Pi*n/2)*(6 - 4*sin(Pi*n/4)) + 4*sqrt(2)*sin(Pi*n/4)*sin(Pi*n/2))/24.
E.g.f.: (cos(x)-cosh(x)-2*sinh(x))/4 + (sqrt(2)*cos(x/sqrt(2))+sin(x/sqrt(2)))*sinh(x/sqrt(2))/6 + 2*exp(x/2)*sinh(x*sqrt(5)/2)/(3*sqrt(5)). (End)
The sequence b(n) = a(n+2) - a(n+1) - a(n) has period 8 and always 0 or 1. - Michael Somos, Nov 06 2015

A093062 a(n) = Fibonacci(prime(n)) - prime(Fibonacci(n)).

Original entry on oeis.org

-1, 0, 2, 8, 78, 214, 1556, 4108, 28518, 513972, 1345808, 24156990, 165578670, 433491846, 2971210580, 53316283380, 956722012572, 2504730758802, 44945570173074, 308061521102198, 806515532933562, 14472334024479534, 99194853094422264, 1779979416004150202
Offset: 1

Views

Author

Dennis S. Kluk (mathemagician(AT)ameritech.net), May 08 2004

Keywords

Comments

Composition of prime( ) and Fibonacci( ) is not commutative. Does a prime p ever divide Fibonacci(prime(p)) - prime(Fibonacci(p))?
Note that a(3) = 2 is the only prime element of the sequence. This is because after 2, all primes are odd; and the Fibonacci number F(n) is even only for n = 3k for some integer k [which relates to the fact that A082115 Fibonacci sequence (mod 3) is periodic with Pisano period 8]. Hence after a(1) = -1, Fibonacci(prime(n)) - prime(Fibonacci(n)) is always the difference of two odd numbers, hence is even. - Jonathan Vos Post, Jan 23 2006
Is a(i) ever divisible by i? Answer: yes. The quotient is an integer for i = 4, 28 and 30 through 63. - Dennis S. Kluk (mathemagician(AT)ameritech.net), Aug 16 2006

Examples

			a(11) = Fibonacci(prime(11)) - prime(Fibonacci(11)) = 1345808.
		

Crossrefs

Programs

  • Magma
    [Fibonacci(NthPrime(n)) - NthPrime(Fibonacci(n)): n in [1..30]]; // Vincenzo Librandi, Apr 10 2020
  • Mathematica
    For[i=1, i<61, i++, Print[i, " ", Fibonacci[Prime[i]]-Prime[Fibonacci[i]]]]
    Table[Fibonacci[Prime[n]]-Prime[Fibonacci[n]],{n,30}] (* Harvey P. Dale, Jul 02 2018 *)
  • PARI
    a(n) = { fibonacci(prime(n)) - prime(fibonacci(n)) } \\ Harry J. Smith, Jun 20 2009
    

Formula

a(n) = Fibonacci(prime(n)) - prime(Fibonacci(n)).

A160079 Lodumo_3 of Fibonacci numbers.

Original entry on oeis.org

0, 1, 4, 2, 3, 5, 8, 7, 6, 10, 13, 11, 9, 14, 17, 16, 12, 19, 22, 20, 15, 23, 26, 25, 18, 28, 31, 29, 21, 32, 35, 34, 24, 37, 40, 38, 27, 41, 44, 43, 30, 46, 49, 47, 33, 50, 53, 52, 36, 55, 58, 56, 39, 59, 62, 61, 42, 64, 67, 65, 45, 68, 71, 70, 48, 73, 76, 74, 51, 77, 80, 79, 54
Offset: 0

Views

Author

Philippe Deléham, May 01 2009

Keywords

Comments

Permutation of nonnegative integers.

Crossrefs

Cf. A000045, A082115, A160016, A160051, A367651 (inverse permutation).

Formula

a(n) = lod_3(A000045(n)).
a(n) = 2*a(n-8) - a(n-16) for n >= 16. - Philippe Deléham, Mar 09 2023
a(8*n) = 6*n, a(8*n+1) = 9*n+1, a(8*n+2) = 9*n+4, a(8*n+3) = 9*n+2, a(8*n+4) = 6*n+3, a(8*n+5) = 9*n+5, a(8*n+6) = 9*n+8, a(8*n+7) = 9*n+7. - Philippe Deléham, Nov 24 2023
From Philippe Deléham, Nov 29 2023 : (Start)
a(n) = a(n-4) + a(n-8) - a(n-12) for n >= 12.
G.f. : (x + 4*x^2 + 2*x^3 + 3*x^4 + 4*x^5 + 4*x^6 + 5*x^7 + 3*x^8 + 4*x^9 + x^10 + 2*x^11) / (1 - x^4 - x^8 + x^12). (End)

A117875 Triangle a(n,m) = (A000045(m) mod 3)+ (A000045(n) mod 7) read by rows.

Original entry on oeis.org

0, 1, 2, 1, 2, 2, 2, 3, 3, 4, 3, 4, 4, 5, 3, 5, 6, 6, 7, 5, 7, 1, 2, 2, 3, 1, 3, 3, 6, 7, 7, 8, 6, 8, 8, 7, 0, 1, 1, 2, 0, 2, 2, 1, 0, 6, 7, 7, 8, 6, 8, 8, 7, 6, 7, 6, 7, 7, 8, 6, 8, 8, 7, 6, 7, 7, 5, 6, 6, 7, 5, 7, 7, 6, 5, 6, 6, 7, 4, 5, 5, 6, 4, 6, 6, 5, 4, 5, 5, 6, 4, 2, 3, 3, 4, 2, 4, 4, 3, 2, 3, 3, 4, 2, 4
Offset: 0

Views

Author

Roger L. Bagula, May 13 2006

Keywords

Examples

			The triangle starts in row n=0 as:
0;
1, 2;
1, 2, 2;
2, 3, 3, 4;
3, 4, 4, 5, 3;
5, 6, 6, 7, 5, 7;
1, 2, 2, 3, 1, 3, 3;
6, 7, 7, 8, 6, 8, 8, 7;
0, 1, 1, 2, 0, 2, 2, 1, 0;
6, 7, 7, 8, 6, 8, 8, 7, 6, 7;
6, 7, 7, 8, 6, 8, 8, 7, 6, 7, 7;
		

Crossrefs

Cf. A000045.

Programs

  • Mathematica
    a[0] = 0; a[1] = 1; a[n_] := a[n] = a[n - 1] + a[n - 2] f[n_, m_] := Mod[a[n], 3] + Mod[a[m], 7] aout = Table[Table[f[n, m], {n, 0, m}], {m, 0, 10}] c = Flatten[aout]

Formula

a(n,m) = A082115(m) + A105870(n).

Extensions

Fuzzy comments removed, formula added, row and column indices disentangled by Assoc. Eds. of the OEIS - Jun 15 2010

A164743 Digital root of 3*A000045(n).

Original entry on oeis.org

3, 3, 6, 9, 6, 6, 3, 9, 3, 3, 6, 9, 6, 6, 3, 9, 3, 3, 6, 9, 6, 6, 3, 9, 3, 3, 6, 9, 6, 6, 3, 9
Offset: 1

Views

Author

Mark Dols, Aug 24 2009

Keywords

Comments

Period 8.

Crossrefs

Formula

a(n+1) = sum of digits of a(n) + a(n-1).
a(n) = A010888(3*A000045(n)). - R. J. Mathar, Nov 03 2016
G.f.: -3*x*(1+x+2*x^2+3*x^3+2*x^4+2*x^5+x^6+3*x^7) / ( (x-1)*(1+x)*(x^2+1)*(x^4+1) ). - R. J. Mathar, Nov 03 2016
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