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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A068858 a(1) = 3 = 1*3; a(n) = smallest multiple of a(n-1) which is a product of two consecutive odd numbers. 1
3, 15, 195, 4095, 2477475, 448422975, 19384876786275, 70676639845770308825475, 11604095937711402889585984522057770447375, 56023729629975618843823135187551800751351023283966800458449243286895375 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

195 = 13*15 belongs to this sequence and the smallest multiple of 195 which is a product of two consecutive odd numbers is 4095 = 63*65.

MAPLE

f:= proc(x) local V, V1, y;

     V:= map(t -> rhs(op(t))-1, [msolve(r^2=1, x)]);

     V:= map(t -> `if`(t*(t+2)=x, t + x, t), V);

     y:= min(map(t -> `if`(t::even, t+x, t), V));

     y*(y+2)

end proc:

A[1]:= 3:

for n from 2 to 11 do A[n]:= f(A[n-1]) od:

seq(A[i], i=1..11); # Robert Israel, May 14 2017

CROSSREFS

Cf. A068857.

Sequence in context: A087614 A063739 A060194 * A280772 A166359 A195515

Adjacent sequences:  A068855 A068856 A068857 * A068859 A068860 A068861

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Mar 12 2002

EXTENSIONS

More terms from Sascha Kurz, Mar 23 2002

Corrected by Robert Israel, May 14 2017

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 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)