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 A332187 a(n) = 8*(10^(2n+1)-1)/9 - 10^n. 3
 7, 878, 88788, 8887888, 888878888, 88888788888, 8888887888888, 888888878888888, 88888888788888888, 8888888887888888888, 888888888878888888888, 88888888888788888888888, 8888888888887888888888888, 888888888888878888888888888, 88888888888888788888888888888, 8888888888888887888888888888888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Table of n, a(n) for n=0..15. Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000). FORMULA a(n) = 8*A138148(n) + 7*10^n = A002282(2n+1) - 10^n. G.f.: (7 + 101*x - 900*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 A332187 := n -> 8*(10^(2*n+1)-1)/9-10^n; MATHEMATICA Array[8 (10^(2 # + 1)-1)/9 - 10^# &, 15, 0] PROG (PARI) apply( {A332187(n)=10^(n*2+1)\9*8-10^n}, [0..15]) (Python) def A332187(n): return 10**(n*2+1)//9*8-10**n CROSSREFS Cf. (A077776-1)/2 = A183190: 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), A002113 (palindromes). Cf. A332117 .. A332197 (variants with different "wing" digit 1, ..., 9). Cf. A332180 .. A332189 (variants with different middle digit 0, ..., 9). Sequence in context: A308296 A193342 A298301 * A093171 A330295 A177908 Adjacent sequences: A332184 A332185 A332186 * A332188 A332189 A332190 KEYWORD nonn,base,easy AUTHOR M. F. Hasler, Feb 08 2020 STATUS approved

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Last modified December 9 09:12 EST 2023. Contains 367690 sequences. (Running on oeis4.)