login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A091789 a(1) = 1, a(2) = 2, a(n) = reverse concatenation of two previous terms. 2
1, 2, 21, 122, 22112, 21122221, 1222211221122, 221122112222112222112, 2112222112222112211222211221122221, 1222211221122221122112222112222112211222211222211221122 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Concatenation of any three successive terms is a palindrome.

LINKS

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

MAPLE

Rcat := proc(a, b) local resul, digs ; digs := convert(b, base, 10) ; resul := 0 ; for k in digs do resul := resul*10+k ; od ; digs := convert(a, base, 10) ; for k in digs do resul := resul*10+k ; od ; RETURN(resul) ; end: A091789 := proc(nmax) local a, anxt, n, i, j; a := [1, 2] ; for n from 3 to nmax do a := [op(a), Rcat(op(-2, a), op(-1, a))] ; od; RETURN(a) ; end: op(A091789(13)) ; # R. J. Mathar, Jul 26 2007

CROSSREFS

Cf. A091790.

Sequence in context: A068045 A188530 A178328 * A109789 A136588 A171009

Adjacent sequences:  A091786 A091787 A091788 * A091790 A091791 A091792

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Feb 18 2004

EXTENSIONS

More terms from R. J. Mathar, Jul 26 2007

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 July 10 12:34 EDT 2020. Contains 335576 sequences. (Running on oeis4.)