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A332185
a(n) = 8*(10^(2n+1)-1)/9 - 3*10^n.
2
5, 858, 88588, 8885888, 888858888, 88888588888, 8888885888888, 888888858888888, 88888888588888888, 8888888885888888888, 888888888858888888888, 88888888888588888888888, 8888888888885888888888888, 888888888888858888888888888, 88888888888888588888888888888, 8888888888888885888888888888888
OFFSET
0,1
FORMULA
a(n) = 8*A138148(n) + 5*10^n = A002282(2n+1) - 3*10^n.
G.f.: (5 + 303*x - 1100*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
A332185 := n -> 8*(10^(2*n+1)-1)/9-3*10^n;
MATHEMATICA
Array[8 (10^(2 # + 1)-1)/9 - 3*10^# &, 15, 0]
PROG
(PARI) apply( {A332185(n)=10^(n*2+1)\9*8-3*10^n}, [0..15])
(Python) def A332185(n): return 10**(n*2+1)//9*8-3*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 only), A002113 (palindromes).
Cf. A332180 .. A332189 (variants with different middle digit 0, ..., 9).
Cf. A332115 .. A332195 (variants with different "wing" digit 1, ..., 9).
Sequence in context: A060713 A198402 A214450 * A085706 A190350 A135084
KEYWORD
nonn,base,easy
AUTHOR
M. F. Hasler, Feb 08 2020
STATUS
approved