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 A006243 Extracting a square root. (Formerly M5412) 4
 198, 7761798, 467613464999866416198, 102249460387306384473056172738577521087843948916391508591105798 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Jeffrey Shallit, personal communication. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..6 E. B. Escott, Rapid method for extracting a square root, Amer. Math. Monthly, 44 (1937), 644-646. FORMULA a(1) = 198, a(n) = a(n-1)^3 - 3*a(n-1). - Sean A. Irvine, Feb 08 2017 a(n) = (99 + 70*sqrt(2))^(3^(n-1)) + (99 - 70*sqrt(2))^(3^(n-1)). - Bruno Berselli, Feb 10 2017 MATHEMATICA RecurrenceTable[{a[1]==198, a[n]==a[n-1]^3 - 3 a[n-1]}, a, {n, 8}] (* Vincenzo Librandi, Feb 09 2017 *) PROG (MAGMA) [n eq 1 select 198 else Self(n-1)^3-3*Self(n-1): n in [1..5]]; // Vincenzo Librandi, Feb 09 2017 CROSSREFS Cf. A006242, A112845 (differs only for the initial 6). Sequence in context: A278017 A270849 A097731 * A171391 A151738 A128312 Adjacent sequences:  A006240 A006241 A006242 * A006244 A006245 A006246 KEYWORD nonn AUTHOR EXTENSIONS Offset changed by Sean A. Irvine, Feb 08 2017 STATUS approved

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Last modified March 20 15:26 EDT 2018. Contains 300986 sequences. (Running on oeis4.)