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.

User: , 0, __

, 0, __'s wiki page.

, 0, __ has authored 3 sequences.

A215257 Number of indecomposable permutations sortable by a double-ended queue.

Original entry on oeis.org

0, 1, 1, 3, 13, 67, 383, 2345, 15069, 100341, 686515, 4797997, 34110765, 245926667, 1793867881, 13214905229, 98177212059, 734746226575, 5534054981071, 41917876423855, 319102504087883, 2440086947417629, 18733909260242195, 144354928765952131, 1116015033661158079, 8654019249571514621, 67292250859412467583, 524583875375437922949
Offset: 0

Views

Author

N. J. A. Sloane, Sep 07 2012. a(0)=0 added by N. J. A. Sloane, Sep 12 2012

Keywords

Comments

Suggested by Peter Doyle in an email message, Sep 04 2012

Links

Crossrefs

Cf. A003319, A182216, A216040, A215252.

Formula

INVERTi transform of A182216.

Extensions

Name clarified by Peter Doyle, Dec 13 2013

A215252 Number of indecomposable permutations sortable using two parallel stacks.

Original entry on oeis.org

0, 1, 1, 3, 12, 56, 289, 1602, 9367, 57075, 359346, 2323416, 15356446, 103389175, 707107627, 4901988047, 34384943850, 243694702311, 1742953208739, 12567593026554, 91280392585747, 667341975412356, 4907899368783645, 36289929612761691, 269660272111724536, 2012845416966620068, 15087243969226496324, 113521159338891300347, 857211201390859034536
Offset: 0

Views

Author

N. J. A. Sloane, Sep 07 2012. a(0)=0 added by N. J. A. Sloane, Sep 12 2012

Keywords

Comments

Suggested by Peter Doyle in an email message, Sep 04 2012

Links

Crossrefs

Cf. A003319, A216040, A182216, A215257.

Formula

INVERTi transform of A216040.

A154473 a(n) = A014486(A154472(n)).

Original entry on oeis.org

842, 11090, 13202, 46882, 60994, 231272004, 198873570440, 266349291297936, 64442911458703648, 3667589230123774528, 3336154829743802737792, 17601566387699271821281536, 1023499990310357893964861952
Offset: 0

Views

Author

Antti Karttunen, with terms a(0)-a(100) also independently computed by Wouter Meeussen, with the given Mathematica program, Jan 11 2009

Keywords

Comments

This sequence gives the parenthesis expressions shown at the upper right corner image of the page 103 of NKS, with the left brackets (black squares) converted to 1's and the right brackets (white squares) converted to 0's and then interpreting each such number as a binary number and converted to decimal. A154474 shows the corresponding binary representations. Compare to A080070, A122242, A122245.

Links

Crossrefs

Cf. A154475, A154476.

Programs

  • Mathematica
    init=e[e[e][e]][e][e]
toDeca[ w_ ]:=FromDigits[ ToExpression[ Characters[ ToString[ w ] ]/.{"e"->Sequence[], "["->"1","]"->"0"} ],2 ]
toDeca /@ NestList[ #/.e[x_ ][y_ ]->x[x[y]]&, init, 100]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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