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A332189
a(n) = 8*(10^(2n+1)-1)/9 + 10^n.
15
9, 898, 88988, 8889888, 888898888, 88888988888, 8888889888888, 888888898888888, 88888888988888888, 8888888889888888888, 888888888898888888888, 88888888888988888888888, 8888888888889888888888888, 888888888888898888888888888, 88888888888888988888888888888, 8888888888888889888888888888888
OFFSET
0,1
FORMULA
a(n) = 8*A138148(n) + 9*10^n = A002282(2n+1) + 10^n.
G.f.: (9 - 101*x - 700*x^2)/((1 - x)(1 - 10*x)(1 - 100*x)).
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
MAPLE
A332189 := n -> 8*(10^(2*n+1)-1)/9+10^n;
MATHEMATICA
Array[8 (10^(2 # + 1)-1)/9 + 10^# &, 15, 0]
PROG
(PARI) apply( {A332189(n)=10^(n*2+1)\9*8+10^n}, [0..15])
(Python) def A332189(n): return 10**(n*2+1)//9*8+10**n
CROSSREFS
Cf. A002275 (repunits R_n = (10^n-1)/9), A002282 (8*R_n), A011557 (10^n).
Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332119 .. A332189 (variants with different "wing" digit 1, ..., 8).
Cf. A332180 .. A332187 (variants with different middle digit 0, ..., 7).
Sequence in context: A225169 A287034 A027878 * A045793 A069054 A283801
KEYWORD
nonn,base,easy
AUTHOR
M. F. Hasler, Feb 08 2020
STATUS
approved