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%I #33 Feb 05 2020 23:55:58
%S 0,1,2,3,5,10,27,49,98,267,485,970,2643,4801,9602,26163,47525,95050,
%T 258987,470449,940898,2563707,4656965,9313930,25378083,46099201,
%U 92198402,251217123,456335045,912670090,2486793147,4517251249,9034502498,24616714347
%N Numbers such that floor(a(n)^2 / 6) is a square.
%C Or: Numbers whose square, with its last base-6 digit dropped, is again a square. (For the three initial terms whose square has only one digit in base 6, this is then meant to yield zero.)
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,10,0,0,-1).
%F a(n) = sqrt(A055851(n)).
%F From _Colin Barker_, Sep 18 2014: (Start)
%F a(n) = 10*a(n-3) - a(n-6) for n > 7.
%F G.f.: -x^2*(x+1)*(3*x^4 + 7*x^3 - 2*x^2 - x - 1) / (x^6-10*x^3+1). (End)
%F a(3n+2) = A001079(n). a(3n) = A087799(n-1). - _R. J. Mathar_, Feb 05 2020
%o (PARI) b=6;for(n=0,2e9,issquare(n^2\b) & print1(n","))
%o (PARI) concat(0, Vec(-x^2*(x+1)*(3*x^4+7*x^3-2*x^2-x-1)/(x^6-10*x^3+1) + O(x^100))) \\ _Colin Barker_, Sep 18 2014
%Y Cf. A023110 (base 10), A204502 (base 9), A204514 (base 8), A204516 (base 7), A204520 (base 5), A004275 (base 4), A055793 (base 3), A055792 (base 2).
%K nonn,easy
%O 1,3
%A _M. F. Hasler_, Jan 15 2012
%E More terms from _Colin Barker_, Sep 18 2014
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