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 A332196 a(n) = 10^(2n+1) - 1 - 3*10^n. 7
 6, 969, 99699, 9996999, 999969999, 99999699999, 9999996999999, 999999969999999, 99999999699999999, 9999999996999999999, 999999999969999999999, 99999999999699999999999, 9999999999996999999999999, 999999999999969999999999999, 99999999999999699999999999999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000). FORMULA a(n) = 9*A138148(n) + 6*10^n. G.f.: (6 + 303*x - 1200*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 A332196 := n -> 10^(n*2+1)-1-3*10^n; MATHEMATICA Array[ 10^(2 # + 1) - 1 - 3*10^# &, 15, 0] FromDigits/@Table[Join[PadLeft[{6}, n, 9], PadRight[{}, n-1, 9]], {n, 30}] (* or *) LinearRecurrence[{111, -1110, 1000}, {6, 969, 99699}, 30] (* Harvey P. Dale, May 03 2021 *) PROG (PARI) apply( {A332196(n)=10^(n*2+1)-1-3*10^n}, [0..15]) (Python) def A332196(n): return 10**(n*2+1)-1-3*10^n CROSSREFS Cf. A002275 (repunits R_n = (10^n-1)/9), A002283 (9*R_n), A011557 (10^n). Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes). Cf. A332116 .. A332186 (variants with different repeated digit 1, ..., 8). Cf. A332190 .. A332197, A181965 (variants with different middle digit 0, ..., 8). Sequence in context: A266598 A250392 A145250 * A024085 A080474 A079190 Adjacent sequences: A332193 A332194 A332195 * A332197 A332198 A332199 KEYWORD nonn,base,easy AUTHOR M. F. Hasler, Feb 08 2020 STATUS approved

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Last modified March 25 23:06 EDT 2023. Contains 361529 sequences. (Running on oeis4.)