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%I #16 Nov 30 2020 12:59:15
%S 0,0,0,1,2,6,12,35,70,204,408,1189,2378,6930,13860,40391,80782,235416,
%T 470832,1372105,2744210,7997214,15994428,46611179,93222358,271669860,
%U 543339720,1583407981,3166815962,9228778026,18457556052,53789260175,107578520350
%N Square roots of [A055872/8]: Their square written in base 8, with some digit appended, is again a square.
%C Base-8 analog of A031150. The square of the terms (= truncated squares A055872) are listed in A204504.
%F G.f. = x^4*(1 + 2*x)/(1 - 6*x^2 + x^4)
%t CoefficientList[Series[(x^4 (1+2x))/(1-6x^2+x^4),{x,0,40}],x] (* _Harvey P. Dale_, Nov 30 2020 *)
%o (PARI) b=8;for(n=1,1e7,issquare(n^2\b) & print1(sqrtint(n^2\b)","))
%o (PARI) a(n)=polcoeff((2*x^5 + x^4)/(x^4 - 6*x^2 + 1+O(x^n)),n)
%Y See also A031149=sqrt(A023110) (base 10), A204502=sqrt(A204503) (base 9), A204514=sqrt(A055872) (base 8), A204516=sqrt(A055859) (base 7), A204518=sqrt(A055851) (base 6), A204520=sqrt(A055812) (base 5), A004275=sqrt(A055808) (base 4), A001075=sqrt(A055793) (base 3), A001541=sqrt(A055792) (base 2).
%K nonn,base
%O 1,5
%A _M. F. Hasler_, Jan 15 2012