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A091789 a(1) = 1, a(2) = 2, a(n) = reverse concatenation of two previous terms. 3
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.
a(17) with 1597 digits is the first term > 10^1000. - Michael S. Branicky, Jul 01 2022
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..16
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
PROG
(Python)
from itertools import count, islice
def agen():
s, t = "1", "2"
yield from [1, 2]
while True:
s, t = t, (s+t)[::-1]
yield int(t)
print(list(islice(agen(), 11))) # Michael S. Branicky, Jul 01 2022
CROSSREFS
Cf. A091790.
Sequence in context: A068045 A188530 A178328 * A109789 A136588 A171009
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Feb 18 2004
EXTENSIONS
More terms from R. J. Mathar, Jul 26 2007
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)