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A117713 a(1)=1, a(2)=3, a(3)=8; for n>=4, a(n) = 10*a(n-3) + 8 (if a(n-3) is odd) or + 9 if a(n-3) is even). 0
1, 3, 8, 18, 38, 89, 189, 389, 898, 1898, 3898, 8989, 18989, 38989, 89898, 189898, 389898, 898989, 1898989, 3898989, 8989898, 18989898, 38989898, 89898989, 189898989, 389898989, 898989898, 1898989898, 3898989898, 8989898989, 18989898989, 38989898989, 89898989898 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From a puzzle (1,3,8,18,?,89,189) given on a civil service test.

LINKS

Table of n, a(n) for n=1..33.

MAPLE

f:=proc(n) option remember; local t1; if n=1 then RETURN(1); fi; if n=2 then RETURN(3); fi; if n=3 then RETURN(8); fi; t1:=10*f(n-3)+8; if f(n-3) mod 2 = 0 then t1:=t1+1; fi; RETURN(t1); end;

CROSSREFS

Sequence in context: A172265 A258272 A117727 * A128552 A238361 A011377

Adjacent sequences: A117710 A117711 A117712 * A117714 A117715 A117716

KEYWORD

nonn

AUTHOR

Louis Ciotti (lciotti(AT)twcny.rr.com), Apr 13 2006

EXTENSIONS

Solution proposed by Mohammed BOUAYOUN (mohammed.bouayoun(AT)yahoo.fr), Apr 14 2006

Another possibility is that 1,3,8,18,?,89,189,... is an erroneous version of A117727. - Hugo van der Sanden, Apr 14 2006

STATUS

approved

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Last modified December 1 05:02 EST 2022. Contains 358454 sequences. (Running on oeis4.)