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 A332181 a(n) = 8*(10^(2n+1)-1)/9 - 7*10^n. 3
 1, 818, 88188, 8881888, 888818888, 88888188888, 8888881888888, 888888818888888, 88888888188888888, 8888888881888888888, 888888888818888888888, 88888888888188888888888, 8888888888881888888888888, 888888888888818888888888888, 88888888888888188888888888888, 8888888888888881888888888888888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000). FORMULA a(n) = 8*A138148(n) + 10^n = A002282(2n+1) - 7*10^n. G.f.: (1 + 707*x - 1500*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 A332181 := n -> 8*(10^(2*n+1)-1)/9-7*10^n; MATHEMATICA Array[8 (10^(2 # + 1)-1)/9 - 7*10^# &, 15, 0] PROG (PARI) apply( {A332181(n)=10^(n*2+1)\9*8-7*10^n}, [0..15]) (Python) def A332181(n): return 10**(n*2+1)//9*8-7*10**n CROSSREFS Cf. (A077776-1)/2 = A183184: indices of primes. Cf. A002275 (repunits R_n = (10^n-1)/9), A002282 (8*R_n), A011557 (10^n). Cf. A138148 (cyclops numbers with binary digits only). Cf. A332121 .. A332191 (variants with different repeated digit 2, ..., 9). Cf. A332180 .. A332189 (variants with different middle digit 0, ..., 9). Sequence in context: A279441 A221748 A105989 * A266059 A020445 A143252 Adjacent sequences:  A332178 A332179 A332180 * A332182 A332183 A332184 KEYWORD nonn,base,easy AUTHOR M. F. Hasler, Feb 08 2020 STATUS approved

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Last modified January 22 10:13 EST 2022. Contains 350481 sequences. (Running on oeis4.)