This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A204513 #10 Mar 30 2012 17:23:05 %S A204513 0,0,0,1,9,36,289,2304,9216,73441,585225,2340900,18653761,148644864, %T A204513 594579456,4737981889,37755210249,151020840996,1203428746081, %U A204513 9589674758400,38358699033600,305666163522721,2435739633423369,9742958533693476,77638002106025089,618668277214777344,2474673108859109376,19719746868766849921,157139306672920022025,628557226691680088100,5008738066664673854881,39912765226644470817024,159651060906577883268096 %N A204513 A204517(n)^2 = floor[A055859(n)/7]: Squares which written in base 7, with some digit appended, yield another square. %C A204513 Base-7 analog of A202303. %F A204513 G.f. = (x^4 + 9*x^5 + 36*x^6 + 34*x^7 + 9*x^8 + 36*x^9 + x^10)/(1 - 255*x^3 + 255*x^6 - x^9) %o A204513 (PARI) b=7;for(n=0,200,issquare(n^2\b) & print1(n^2\b,",")) %o A204513 (PARI) A204513(n)=polcoeff((x^4 + 9*x^5 + 36*x^6 + 34*x^7 + 9*x^8 + 36*x^9 + x^10)/(1 - 255*x^3 + 255*x^6 - x^9+O(x^n)),n) %Y A204513 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 A204513 nonn,base %O A204513 1,5 %A A204513 _M. F. Hasler_, Jan 15 2012