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 A093112 a(n) = (2^n-1)^2 - 2. 7
 -1, 7, 47, 223, 959, 3967, 16127, 65023, 261119, 1046527, 4190207, 16769023, 67092479, 268402687, 1073676287, 4294836223, 17179607039, 68718952447, 274876858367, 1099509530623, 4398042316799, 17592177655807, 70368727400447, 281474943156223, 1125899839733759 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Cletus Emmanuel calls these "Carol numbers". LINKS Michael De Vlieger, Table of n, a(n) for n = 1..1660 Amelia Carolina Sparavigna, Binary Operators of the Groupoids of  OEIS A093112 and A093069 Numbers(Carol and Kynea Numbers), Department of Applied Science and Technology, Politecnico di Torino (Italy, 2019). Amelia Carolina Sparavigna, Some Groupoids and their Representations by Means of Integer Sequences, International Journal of Sciences (2019) Vol. 8, No. 10. Eric Weisstein's World of Mathematics, Near-Square Prime Index entries for linear recurrences with constant coefficients, signature (7,-14,8). FORMULA a(n) = (2^n-1)^2 - 2. From Colin Barker, Jul 07 2014: (Start) a(n) = 6*a(n-1) - 7*a(n-2) - 6*a(n-3) + 8*a(n-4). G.f.: x*(16*x^2-14*x+1) / ((x-1)*(2*x-1)*(4*x-1)). (End) E.g.f.: 2 - exp(x) - 2*exp(2*x) + exp(4*x). - Stefano Spezia, Dec 09 2019 MAPLE seq((Stirling2(n+1, 2))^2-2, n=1..23); # Zerinvary Lajos, Dec 20 2006 MATHEMATICA lst={}; Do[p=(2^n-1)^2-2; AppendTo[lst, p], {n, 66}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 27 2008 *) Rest@ CoefficientList[Series[x (16 x^2 - 14 x + 1)/((x - 1) (2 x - 1) (4 x - 1)), {x, 0, 25}], x] (* Michael De Vlieger, Dec 09 2019 *) PROG (PARI) Vec(x*(16*x^2-14*x+1)/((x-1)*(2*x-1)*(4*x-1)) + O(x^100)) \\ Colin Barker, Jul 07 2014 (PARI) a(n) = (2^n-1)^2-2 \\ Charles R Greathouse IV, Sep 10 2015 (Python) def A093112(n): return (2**n-1)**2-2 # Chai Wah Wu, Feb 18 2022 CROSSREFS Cf. A000225. Sequence in context: A201437 A202509 A009202 * A091516 A064385 A269520 Adjacent sequences: A093109 A093110 A093111 * A093113 A093114 A093115 KEYWORD sign,easy AUTHOR Eric W. Weisstein, Mar 20 2004 EXTENSIONS More terms from Colin Barker, Jul 07 2014 STATUS approved

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Last modified March 25 01:20 EDT 2023. Contains 361511 sequences. (Running on oeis4.)