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 A332142 a(n) = 4*(10^(2*n+1)-1)/9 - 2*10^n. 1
 2, 424, 44244, 4442444, 444424444, 44444244444, 4444442444444, 444444424444444, 44444444244444444, 4444444442444444444, 444444444424444444444, 44444444444244444444444, 4444444444442444444444444, 444444444444424444444444444, 44444444444444244444444444444, 4444444444444442444444444444444 (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) = 4*A138148(n) + 2*10^n = A002278(2n+1) - 2*10^n = 2*A332121(n). G.f.: (2 + 202*x - 600*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 A332142 := n -> 4*(10^(2*n+1)-1)/9-2*10^n; MATHEMATICA Array[4 (10^(2 # + 1)-1)/9 - 2*10^# &, 15, 0] PROG (PARI) apply( {A332142(n)=10^(n*2+1)\9*4-2*10^n}, [0..15]) (Python) def A332142(n): return 10**(n*2+1)//9*4-2*10**n CROSSREFS Cf. A002275 (repunits R_n = (10^n-1)/9), A002278 (4*R_n), A011557 (10^n). Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes). Cf. A332112 .. A332192 (variants with different repeated digit 1, ..., 9). Cf. A332140 .. A332149 (variants with different middle digit 0, ..., 9). Sequence in context: A080392 A154541 A119120 * A109931 A352498 A326364 Adjacent sequences: A332139 A332140 A332141 * A332143 A332144 A332145 KEYWORD nonn,base,easy AUTHOR M. F. Hasler, Feb 09 2020 STATUS approved

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Last modified March 27 02:29 EDT 2023. Contains 361553 sequences. (Running on oeis4.)