login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A000661 Shifts 2 places left under boustrophedon transform. 2
1, 0, 1, 1, 2, 6, 17, 62, 259, 1230, 6592, 39313, 258575, 1860318, 14538245, 122670593, 1111715644, 10771412394, 111125142979, 1216309735378, 14078811306851, 171837279141312, 2205768169095338, 29707098687614285 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

REFERENCES

G. W. Hill, Acta Mathematica, VIII (1886).

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..480

J. Millar, N. J. A. Sloane and N. E. Young, A new operation on sequences: the Boustrophedon on transform, J. Combin. Theory, 17A 44-54 1996 (Abstract, pdf, ps).

N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).

N. J. A. Sloane, Transforms

Index entries for sequences related to boustrophedon transform

FORMULA

E.g.f. satisfies: A''(x) - (sec(x)+tan(x))*A(x) = 0 [G. W. Hill, 1886]. - Sergei N. Gladkovskii, Jun 12 2015

a(n) ~ n! * c * 2^n / (n^2 * Pi^n), where c = 21.874759697041762375842937403900898702204499795794357035182354071514... . - Vaclav Kotesovec, Jun 12 2015

MATHEMATICA

nmax = 30; sectan = Normal[Series[Sec[x] + Tan[x], {x, 0, nmax+1}]]; Subscript[a, 0]=1; Subscript[a, 1]=0; egf = Sum[Subscript[a, k]*x^k, {k, 0, nmax+1}]; Table[Subscript[a, k]*k!, {k, 0, nmax}] /.Solve[Take[CoefficientList[Expand[ sectan*egf - D[egf, {x, 2}]], x], nmax-1] == ConstantArray[0, nmax-1]][[1]] (* Vaclav Kotesovec, Jun 12 2015 *)

CROSSREFS

Sequence in context: A000687 A085827 A150035 * A150036 A150037 A150038

Adjacent sequences:  A000658 A000659 A000660 * A000662 A000663 A000664

KEYWORD

nonn,eigen

AUTHOR

N. J. A. Sloane.

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 11:06 EDT 2018. Contains 316379 sequences. (Running on oeis4.)