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 A332126 a(n) = 2*(10^(2n+1)-1)/9 + 4*10^n. 3
 6, 262, 22622, 2226222, 222262222, 22222622222, 2222226222222, 222222262222222, 22222222622222222, 2222222226222222222, 222222222262222222222, 22222222222622222222222, 2222222222226222222222222, 222222222222262222222222222, 22222222222222622222222222222, 2222222222222226222222222222222 (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) = 2*A138148(n) + 6*10^n = A002276(2n+1) + 4*10^n = 2*A332113(n). G.f.: (6 - 404*x + 200*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 A332126 := n -> 2*(10^(2*n+1)-1)/9+4*10^n; MATHEMATICA Array[2 (10^(2 # + 1)-1)/9 + 4*10^# &, 15, 0] Table[FromDigits[Join[PadRight[{}, n, 2], {6}, PadRight[{}, n, 2]]], {n, 0, 20}] (* or *) LinearRecurrence[{111, -1110, 1000}, {6, 262, 22622}, 20] (* Harvey P. Dale, Oct 17 2021 *) PROG (PARI) apply( {A332126(n)=10^(n*2+1)\9*2+4*10^n}, [0..15]) (Python) def A332126(n): return 10**(n*2+1)//9*2+4*10**n CROSSREFS Cf. A002275 (repunits R_n = (10^n-1)/9), A002276 (2*R_n), A011557 (10^n). Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes). Cf. A332116 .. A332196 (variants with different repeated digit 1, ..., 9). Cf. A332120 .. A332129 (variants with different middle digit 0, ..., 9). Sequence in context: A225166 A003384 A316393 * A229579 A033289 A244493 Adjacent sequences: A332123 A332124 A332125 * A332127 A332128 A332129 KEYWORD nonn,base,easy AUTHOR M. F. Hasler, Feb 09 2020 STATUS approved

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Last modified March 31 18:36 EDT 2023. Contains 361672 sequences. (Running on oeis4.)