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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A220449 Define u(n) as in A220448; then a(1)=1, thereafter a(n) = u(n)*a(n-1). 5
1, 1, -10, 10, 190, -730, -6620, 55900, 365300, -5864300, -28269800, 839594600, 2691559000, -159300557000, -238131478000, 38894192662000, -15194495654000, -11911522255750000, 29697351895900000, 4477959179352100000, -21683886333440500000, -2029107997508660900000, 15145164178973569000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The reason for including this sequence as well as A105750 is that the values of this sequence modulo various primes are of interest (see Moll).

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..100

V. H. Moll, An arithmetic conjecture on a sequence of arctangent sums, 2012. See f_n.

FORMULA

A105750(n) = (-1)^(n+1)*a(n).

Define x(n) as in A220447. Then x(n) = (a(n+1)+a(n))/((n+1)*a(n)).

MAPLE

x:=proc(n) option remember;

if n=1 then 1 else (x(n-1)+n)/(1-n*x(n-1)); fi; end;

f:=proc(n) option remember; global x;

if n = 1 then 1 else n*x(n-1)*f(n-1)-f(n-1); fi; end;

[seq(f(n), n=1..30)];

CROSSREFS

Cf. A105750, A220446, A220447, A220448, A220450, A220451.

Sequence in context: A047817 A065243 A105750 * A318968 A288051 A288504

Adjacent sequences:  A220446 A220447 A220448 * A220450 A220451 A220452

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Dec 22 2012

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)