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.

Previous Showing 11-16 of 16 results.

A005204 Coding a recurrence.

Original entry on oeis.org

0, 0, 0, 1, 2, 4, 9, 38, 308, 4937, 316006, 161795380, 1325427757897, 694905868332618342, 186537373642942364470529332, 410200022670422956346283949740775609161, 472928427326946774459561651845917849178636866326243365478
Offset: 0

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Author

Keywords

Comments

Consider a rabbits generation tree, and code each level with 0 for a single segment, and 1 for a branched segment. The current sequence written in binary: 0, 0, 0, 1, 10, 100, is obtained with this scheme applied on sequence A000930, and follows recurrence formula a(n+3) = 2^A000930(n-1)*a(n+2) + a(n), when n >= 3. Note that the Fib. Quart. article gives incorrect value of 158022 for a(10). - Michel Marcus, Jul 29 2013

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A005203 (same kind of encoding).

Programs

  • PARI
    A000930(n) = sum(i=0, n\3, binomial(n-2*i, i))
    a(n) =  if (n==0, 0, if (n==1, 0, if (n==2, 0, if (n==3, 1, 2^A000930(n-4)*a(n-1) + a(n-3))))) \\ Michel Marcus, Jul 29 2013

Extensions

a(10) corrected and sequence extended by Michel Marcus, Jul 29 2013
More terms from Eric M. Schmidt, Jul 11 2015

A144288 Fibonacci rabbit sequence number n coded in base n, also diagonal of A144287.

Original entry on oeis.org

1, 2, 10, 276, 81901, 2247615258, 81658169024988865, 644986443956439734064225751112, 3427833941153173630835645403655873661712817810325122
Offset: 1

Views

Author

Alois P. Heinz, Sep 17 2008

Keywords

Crossrefs

Programs

  • Maple
    f:= proc(n, b) option remember; `if`(n<2, [n, n], [f(n-1, b)[1] *b^f(n-1, b)[2] +f(n-2, b)[1], f(n-1, b)[2] +f(n-2, b)[2]]) end: a:= n-> f(n, n)[1]: seq(a(n), n=1..11);
  • Mathematica
    f[n_, b_] := f[n, b] = If[n < 2, {n, n}, {f[n-1, b][[1]]*b^f[n-1, b][[2]] + f[n-2, b][[1]], f[n-1, b][[2]] + f[n-2, b][[2]]}]; a[n_] := f[n, n][[1]]; Table[a[n], {n, 1, 9}] (* Jean-François Alcover, Jan 03 2013, translated from Maple *)

Formula

See program.

A162438 a(1)=1, a(2)=2. Take terms a(n-1) and a(n-2), then convert to binary. Concatenate them, with either binary a(n-1) on the left and a(n-2) on the right, or with a(n-1) on the right and a(n-2) on the left such that the value of the resulting binary number is maximized. a(n) = the decimal equivalent of the resulting binary number.

Original entry on oeis.org

1, 2, 6, 26, 218, 7002, 1792858, 14687099738, 30801080592587610, 529158535306496354546309978, 19064945459410035469668296404984822042942298
Offset: 1

Views

Author

Leroy Quet, Jul 03 2009

Keywords

Comments

The difference between A162438(n) - A162437(n): 0, 0, 1, 5, 45, 1453, 372141, 3048582573, ..., . - Robert G. Wilson v, Jul 27 2009

Examples

			The binary representation of the first few terms: 1, 10, 110, 11010, 11011010.
		

Crossrefs

Programs

  • Mathematica
    a[1] = 1; a[2] = 2; a[n_] := Block[ {a1 = IntegerDigits[a[n - 1], 2], a2 = IntegerDigits[ a[n - 2], 2]}, Max[ FromDigits[ Join[a1, a2], 2], FromDigits[ Join[a2, a1], 2]]]; Array[a, 13] (* Robert G. Wilson v, Jul 27 2009 *)

Extensions

More terms from Robert G. Wilson v, Jul 27 2009

A065353 Decimal representation of palindromes extracted from the Golden String using ever increasing Fibonacci-style subdivisions.

Original entry on oeis.org

1, 0, 3, 2, 27, 90, 7003, 744282, 14687099739, 12786682083105626, 529158535306496354546309979, 7914572860144723898900437268660641289952090
Offset: 0

Views

Author

Patrick De Geest, Oct 31 2001

Keywords

Comments

A zero must be prefixed to the 2n (n>0) terms when converting back to binary.

Examples

			Bin (Dec) -> 1 (1); 0 (0); 11 (3); 010 (2); 11011 (27); 01011010 (90); 1101101011011 (7003); 010110101101101011010 (744282); etc.
		

Crossrefs

A065354 Decimal representation of binary palindromes extracted from the Golden String using ever-increasing Lucas-style subdivisions.

Original entry on oeis.org

1, 5, 6, 107, 730, 224091, 190536538, 120316721060699, 26815615903949132618586, 9090874414162652716478489106641017691, 285152539069955354427985396951391834474389843433339258362714
Offset: 1

Views

Author

Patrick De Geest, Oct 31 2001

Keywords

Comments

A zero must be prefixed to the 2n+1 terms (n>0) when converting back to binary.

Examples

			Bin (Dec) -> {10} skipped -> start: 1 (1); 101 (5); 0110 (6); 1101011 (107); 01011011010 (730); 110110101101011011 (224091); etc.
		

Crossrefs

A162437 a(1)=1, a(2)=2. Take terms a(n-1) and a(n-2), then convert to binary. Concatenate them, with either binary a(n-1) on the left and a(n-2) on the right, or with a(n-1) on the right and a(n-2) on the left such that the value of the resulting binary number is minimized. a(n) = the decimal equivalent of the resulting binary number.

Original entry on oeis.org

1, 2, 5, 21, 173, 5549, 1420717, 11638517165, 24407739551034797, 419321772563920711635545517, 15107659029337673520218077770654501397966253
Offset: 1

Views

Author

Leroy Quet, Jul 03 2009

Keywords

Examples

			The binary representation of the first few terms: 1, 10, 101, 10101, 10101101
		

Crossrefs

Programs

  • Mathematica
    a[1] = 1; a[2] = 2; a[n_] := Block[{a1 = IntegerDigits[ a[n - 1], 2], a2 = IntegerDigits[ a[n - 2], 2]}, Min[ FromDigits[ Join[a1, a2], 2], FromDigits[ Join[a2, a1], 2]]]; Array[a, 13] (* Robert G. Wilson v, Jul 27 2009 *)

Extensions

More terms from Robert G. Wilson v, Jul 27 2009
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