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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A057361 a(n) = floor(5*n/8).

Original entry on oeis.org

0, 0, 1, 1, 2, 3, 3, 4, 5, 5, 6, 6, 7, 8, 8, 9, 10, 10, 11, 11, 12, 13, 13, 14, 15, 15, 16, 16, 17, 18, 18, 19, 20, 20, 21, 21, 22, 23, 23, 24, 25, 25, 26, 26, 27, 28, 28, 29, 30, 30, 31, 31, 32, 33, 33, 34, 35, 35, 36, 36, 37, 38, 38, 39, 40, 40, 41, 41, 42, 43, 43, 44, 45, 45
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Programs

  • Magma
    [Floor(5*n/8): n in [0..50]]; // G. C. Greubel, Nov 02 2017
  • Mathematica
    Floor[(5*Range[0,80])/8] (* or *) LinearRecurrence[{1,0,0,0,0,0,0,1,-1},{0,0,1,1,2,3,3,4,5},80] (* Harvey P. Dale, Jul 18 2013 *)
  • PARI
    a(n)=5*n\8 \\ Charles R Greathouse IV, Sep 02 2015
    

Formula

G.f. x^2*(1+x^2+x^3+x^5+x^6) / ( (1+x)*(x^2+1)*(x^4+1)*(x-1)^2 ). - Numerator corrected Feb 20 2011
a(0)=0, a(1)=0, a(2)=1, a(3)=1, a(4)=2, a(5)=3, a(6)=3, a(7)=4, a(8)=5, a(n)=a(n-1)+a(n-8)-a(n-9). - Harvey P. Dale, Jul 18 2013
Sum_{n>=2} (-1)^n/a(n) = sqrt(2*(1+1/sqrt(5)))*Pi/10 - log(phi)/sqrt(5), where phi is the golden ratio (A001622). - Amiram Eldar, Sep 30 2022

A057362 a(n) = floor(5*n/13).

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 9, 9, 10, 10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 15, 16, 16, 16, 17, 17, 18, 18, 18, 19, 19, 20, 20, 20, 21, 21, 21, 22, 22, 23, 23, 23, 24, 24, 25, 25, 25, 26, 26, 26, 27, 27, 28, 28, 28, 29
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Programs

  • Magma
    [Floor(5*n/13): n in [0..50]]; // G. C. Greubel, Nov 02 2017
  • Mathematica
    Table[Floor[5*n/13], {n, 0, 50}] (* G. C. Greubel, Nov 02 2017 *)
    LinearRecurrence[{1,0,0,0,0,0,0,0,0,0,0,0,1,-1},{0,0,0,1,1,1,2,2,3,3,3,4,4,5},80] (* Harvey P. Dale, Dec 12 2021 *)
  • PARI
    a(n)=5*n\13 \\ Charles R Greathouse IV, Sep 02 2015
    

Formula

G.f.: x^3*(1 + x^3 + x^5 + x^8 + x^10) / ( (x^12 + x^11 + x^10 + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x-1)^2 ). [Numerator corrected Feb 20 2011]
Sum_{n>=3} (-1)^(n+1)/a(n) = sqrt(1-2/sqrt(5))*Pi/5 + arccosh(7/2)/(2*sqrt(5)) + log(2)/5. - Amiram Eldar, Sep 30 2022

A057363 a(n) = floor(8*n/13).

Original entry on oeis.org

0, 0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 10, 11, 11, 12, 12, 13, 14, 14, 15, 16, 16, 17, 17, 18, 19, 19, 20, 20, 21, 22, 22, 23, 24, 24, 25, 25, 26, 27, 27, 28, 28, 29, 30, 30, 31, 32, 32, 33, 33, 34, 35, 35, 36, 36, 37, 38, 38, 39, 40, 40, 41, 41, 42, 43, 43, 44, 44
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Note that 20 appears twice. Different from A005206, A060143.

Programs

  • Magma
    [Floor(8*n/13): n in [0..50]]' // G. C. Greubel, Nov 02 2017
  • Mathematica
    Table[Floor[8*n/13], {n, 0, 50}] (* G. C. Greubel, Nov 02 2017 *)
    LinearRecurrence[{1,0,0,0,0,0,0,0,0,0,0,0,1,-1},{0,0,1,1,2,3,3,4,4,5,6,6,7,8},80] (* Harvey P. Dale, Jul 21 2020 *)
  • PARI
    a(n)=8*n\13 \\ Charles R Greathouse IV, Sep 02 2015
    

Formula

a(n) = a(n-1) + a(n-13) - a(n-14).
G.f.: x^2*(1+x)*(x^2 - x + 1)*(x^8 + x^7 + x^2 + 1)/( (x^12 + x^11 + x^10 + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x-1)^2 ). [Numerator corrected Feb 20 2011]

A057364 a(n) = floor(8*n/21).

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11, 11, 11, 12, 12, 12, 13, 13, 14, 14, 14, 15, 15, 16, 16, 16, 17, 17, 17, 18, 18, 19, 19, 19, 20, 20, 20, 21, 21, 22, 22, 22, 23, 23, 24, 24, 24, 25, 25, 25, 26, 26, 27, 27, 27, 28, 28, 28, 29
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Programs

Formula

a(n) = a(n-1) + a(n-21) - a(n-22).
G.f.: x^3*(1+x)*(x^4 - x^3 + x^2 - x + 1)*(x^13 + x^11 + x^3 + 1) / ( (1 + x + x^2)*(x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x^12 - x^11 + x^9 - x^8 + x^6 - x^4 + x^3 - x + 1)*(x-1)^2 ). [Numerator corrected by R. J. Mathar, Feb 20 2011]

A057365 a(n) = floor(13*n/21).

Original entry on oeis.org

0, 0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 10, 11, 11, 12, 13, 13, 14, 14, 15, 16, 16, 17, 17, 18, 19, 19, 20, 21, 21, 22, 22, 23, 24, 24, 25, 26, 26, 27, 27, 28, 29, 29, 30, 30, 31, 32, 32, 33, 34, 34, 35, 35, 36, 37, 37, 38, 39, 39, 40, 40, 41, 42, 42, 43, 43, 44, 45
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Programs

Formula

a(n) = a(n-1) + a(n-21) - a(n-22).
G.f.: x^2*(1 + x^2 + x^3 + x^5 + x^7 + x^8 + x^10 + x^11 + x^13 + x^15 + x^16 + x^18 + x^19)/( (1+x+x^2)*(x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x^12 - x^11 + x^9 - x^8 + x^6 - x^4 + x^3 - x + 1)*(x-1)^2 ). [Numerator corrected Feb 20 2011]

A057366 a(n) = floor(7*n/19).

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11, 11, 11, 12, 12, 12, 13, 13, 14, 14, 14, 15, 15, 15, 16, 16, 16, 17, 17, 18, 18, 18, 19, 19, 19, 20, 20, 21, 21, 21, 22, 22, 22, 23, 23, 23, 24, 24, 25, 25, 25, 26, 26, 26, 27, 27, 28, 28
Offset: 0

Views

Author

Keywords

Comments

The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.

References

  • N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.

Crossrefs

Similar pattern in Hebrew leap years A057349. Floors of other ratios: A004526, A002264, A002265, A004523, A057353, A057354, A057355, A057356, A057357, A057358, A057359, A057360, A057361, A057362, A057363, A057364, A057365, A057366, A057367.

Programs

Formula

a(n) = a(n-1) + a(n-19) - a(n-20).
G.f.: x^3*(x^2-x+1)*(x^14 + x^13 + x^12 - x^10 + x^8 + x^7 + x^6 + x + 1)/( (x^18 + x^17 + x^16 + x^15 + x^14 + x^13 + x^12 + x^11 + x^10 + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x + 1)*(x-1)^2 ). [Corrected by R. J. Mathar, Feb 20 2011]

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).

A132270 a(n) = floor((n^7-1)/(7*n^6)), which is the same as integers repeated 7 times.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10
Offset: 1

Views

Author

Mohammad K. Azarian, Nov 06 2007

Keywords

Crossrefs

Cf. A004526 ([n/2]), A002264 ([n/3]), A002265 ([n/4]), A002266 ([n/5]), A054895.
Cf. A152467 ([n/6]), A132292 ([(n-1)/8]).
Cf. A002162.

Programs

Formula

a(n) = floor((n^7-n^6)/(7*n^6-6*n^5)). - Mohammad K. Azarian, Nov 08 2007
G.f.: x^8/(1-x-x^7+x^8). - Robert Israel, Feb 02 2015
a(n) = a(n-1)+a(n-7)-a(n-8). - Wesley Ivan Hurt, May 03 2021
a(n) = floor((n-1)/7). - M. F. Hasler, May 19 2021
Sum_{n>=8} (-1)^n/a(n) = log(2) (A002162). - Amiram Eldar, Sep 30 2022

Extensions

Offset corrected by Mohammad K. Azarian, Nov 19 2008

A185204 Triangular array D(n,k) counting disconnected k-regular simple graphs on n vertices with girth at least 4.

Original entry on oeis.org

0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 2, 1, 0, 2, 1, 1, 4, 1, 1, 0, 4, 0, 1, 1, 6, 2, 1, 0, 7, 0, 1, 1, 10, 9, 1, 1, 0, 11, 0, 0, 1, 1, 15, 35, 2, 1, 0, 17, 0, 2, 1, 1, 23, 177, 15, 1, 1, 0, 26, 0, 35, 0, 1, 1, 33, 1153, 247, 1, 1, 0, 38, 0, 1692, 0, 1, 1, 49, 10341, 17409, 8, 1
Offset: 1

Views

Author

Jason Kimberley, Feb 22 2011

Keywords

Comments

For n >= 0 and 0 <= k <= A002265(n).

Examples

			0;
1;
1;
1, 1;
1, 0;
1, 1;
1, 0;
1, 1, 1;
1, 0, 1;
1, 1, 2;
1, 0, 2;
1, 1, 4, 1;
1, 0, 4, 0;
1, 1, 6, 2;
1, 0, 7, 0;
1, 1, 10, 9, 1;
1, 0, 11, 0, 0;
1, 1, 15, 35, 2;
1, 0, 17, 0, 2;
		

Crossrefs

Disconnected k-regular simple graphs with girth at least 4: A185214 (any k), this sequence (triangle); specified degree k: A185224 (k=2), A185234 (k=3), A185244 (k=4), A185254 (k=5), A185264 (k=6), A185274 (k=7), A185284 (k=8), A185294 (k=9).

Extensions

The b-file corrected and a-file expanded by the author, Jan 19 2013

A208970 T(n,k) is the number of n-bead necklaces labeled with numbers -k..k allowing reversal, with sum zero and first and second differences in -k..k.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 1, 1, 2, 2, 4, 3, 2, 1, 2, 2, 8, 9, 8, 2, 1, 2, 5, 11, 19, 29, 15, 4, 1, 3, 5, 18, 40, 90, 87, 42, 4, 1, 3, 5, 24, 77, 221, 371, 325, 94, 7, 1, 3, 8, 35, 130, 495, 1185, 1755, 1148, 246, 7, 1, 3, 8, 45, 213, 967, 3186, 6883, 8092, 4168, 613, 14, 1
Offset: 1

Views

Author

R. H. Hardin, Mar 03 2012

Keywords

Comments

Table starts
.1..1...1....1....1.....1.....1......1......1......1.......1.......1......1
.1..1...1....2....2.....2.....2......3......3......3.......3.......4......4
.1..1...2....2....2.....5.....5......5......8......8.......8......13.....13
.1..3...4....8...11....18....24.....35.....45.....61......76......98....119
.1..3...9...19...40....77...130....213....325....484.....687.....956...1294
.2..8..29...90..221...495...967...1801...3093...5050....7921...11994..17488
.2.15..87..371.1185..3186..7425..15658..30368..55222...95087..156612.248194
.4.42.325.1755.6883.21830.58791.140429.304536.612054.1154448.2066531

Examples

			Some solutions for n=5, k=5:
.-2...-2...-1...-3...-2...-1...-2...-2...-2...-1...-2...-1...-3...-1...-2...-2
.-2...-1....0...-2...-1...-1...-1....0....0....0....0....0...-1....0....0...-2
..0....1....1....2....2....0....2...-1....2...-1....1....0....2....0....0...-1
..2....2...-1....2....1....2....0....2...-1....0....1....0....3....1....2....3
..2....0....1....1....0....0....1....1....1....2....0....1...-1....0....0....2
		

Crossrefs

Row 2 is A002265(n+4).
Row 3 is A000982(floor(n/3)+1).

Formula

Empirical for row n:
n=2: a(k) = a(k-1) + a(k-4) - a(k-5).
n=3: a(k) = a(k-1) + a(k-3) - a(k-4) + a(k-6) - a(k-7) - a(k-9) + a(k-10).
n=4: a(k) = 2*a(k-1) + a(k-2) - 4*a(k-3) + a(k-4) + 2*a(k-5) - a(k-6).
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