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 1-3 of 3 results.

A058182 a(n) = a(n-1)^2 + a(n-2) for n >= 2 with a(0) = 1 and a(1) = 0.

Original entry on oeis.org

1, 0, 1, 1, 2, 5, 27, 734, 538783, 290287121823, 84266613096281243382112, 7100862082718357559748563880517486086728702367, 50422242317787290639189291009890702507917377925161079229314384058371278254659634544914784801
Offset: 0

Views

Author

Henry Bottomley, Nov 15 2000

Keywords

Comments

Has property that CONTINUANT([1, 1, 2, 5, 27, 734, 538783, ...]) = [1, 2, 5, 27, 734, 538783, ...]. - N. J. A. Sloane Jul 19 2002
For n > 2, a(n) is the numerator of the simplified continued fraction resulting from [a(2), a(3), ..., a(n)]. Therefore, for n > 2, a(n) represents the number of ways to tile a (n-2)-board with dominoes and stackable squares, where nothing can be stacked on a domino but otherwise for 2 < i < n, the i-th cell may be stacked by as many as a(i) squares (see Benjamin, A. and Quinn, J.). - Melvin Peralta, Feb 22 2016

Examples

			a(6) = a(5)^2 + a(4) = 5^2 + 2 = 27.
		

References

  • Arthur Benjamin and Jennifer Quinn, Proofs that Really Count, Mathematical Association of America, 2003, see pages 49-51.

Crossrefs

Programs

  • Magma
    I:=[1,0]; [n le 2 select I[n] else Self(n-1)^2+Self(n-2): n in [1..13]]; // Vincenzo Librandi, Feb 23 2016
  • Mathematica
    Join[{a=1,b=0},Table[c=a+b^2;a=b;b=c,{n,12}]] (* Vladimir Joseph Stephan Orlovsky, Jan 22 2011 *)
    Join[{1},Transpose[NestList[{Last[#],Last[#]^2+First[#]}&,{0,1},12]][[1]]] (* Harvey P. Dale, May 15 2011 *)
    RecurrenceTable[{a[0] == 1, a[1] == 0, a[n] == a[n-1]^2 + a[n-2]}, a, {n, 13}] (* Vincenzo Librandi, Feb 23 2016 *)
  • PARI
    a(n)=if(n<0, -a(-1-n), if(n<2, 1-n, a(n-1)^2+a(n-2))) /* Michael Somos, May 05 2005 */
    

Formula

a(n)^2 = a(n+1) - a(n-1), a(-1-n) = -a(n).
For n > 1, a(n+1) = floor(c^(2^n)) where c=1.108604586393628626769904017539.... - Benoit Cloitre, Nov 30 2002
a(n+1) = a(n)^2 + floor(sqrt(a(n))) = A000290(a(n)) + A000196(a(n)) for n > 2. - Reinhard Zumkeller, May 16 2006

Extensions

More terms from Reinhard Zumkeller, May 16 2006

A243139 a(n) = 2^prime(n) + prime(n).

Original entry on oeis.org

6, 11, 37, 135, 2059, 8205, 131089, 524307, 8388631, 536870941, 2147483679, 137438953509, 2199023255593, 8796093022251, 140737488355375, 9007199254741045, 576460752303423547, 2305843009213694013, 147573952589676412995, 2361183241434822606919
Offset: 1

Views

Author

Vincenzo Librandi, Jun 03 2014

Keywords

Crossrefs

Programs

  • Magma
    [2^p + p: p in PrimesUpTo(80)];
  • Mathematica
    f[n_]:=(2^Prime[n] + Prime[n]); Array[f, 80, 1]

A259984 a(n) = A000787(n) + 1.

Original entry on oeis.org

1, 2, 9, 12, 70, 89, 97, 102, 112, 182, 610, 620, 690, 809, 819, 889, 907, 917, 987, 1002, 1112, 1692, 1882, 1962, 6010, 6120, 6700, 6890, 6970, 8009, 8119, 8699, 8889, 8969, 9007, 9117, 9697, 9887, 9967, 10002, 10102, 10802, 11012, 11112, 11812, 16092
Offset: 1

Views

Author

N. J. A. Sloane, Jul 13 2015

Keywords

Crossrefs

Cf. A000787.
Showing 1-3 of 3 results.