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 A204503 Squares n^2 such that floor(n^2/9) is again a square. 20
 0, 1, 4, 9, 16, 36, 81, 144, 225, 324, 441, 576, 729, 900, 1089, 1296, 1521, 1764, 2025, 2304, 2601, 2916, 3249, 3600, 3969, 4356, 4761, 5184, 5625, 6084, 6561, 7056, 7569, 8100, 8649, 9216, 9801, 10404, 11025, 11664, 12321, 12996, 13689, 14400, 15129, 15876 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Or: Squares which remain squares when their last base-9 digit is dropped. (For the first three terms, which have only 1 digit in base 9, dropping that digit is meant to yield zero.) Base-9 analog of A055792 (base 2), A055793 (base 3), A055808 (base 4), A055812 (base 5), A055851 (base 6), A055859 (base 7), A055872(base 8) and A023110 (base 10). LINKS M. F. Hasler, Truncated squares, OEIS wiki, Jan 16 2012 FORMULA a(n) = A204502(n)^2. Conjectures: a(n) = 9*(n-4)^2 for n>5. G.f.: x^2*(7*x^6-12*x^5-11*x^4-x-1) / (x-1)^3. - Colin Barker, Sep 15 2014 MATHEMATICA Select[Range[0, 200]^2, IntegerQ[Sqrt[Floor[#/9]]]&] (* Harvey P. Dale, Jan 27 2012 *) PROG (PARI) b=9; for(n=1, 200, issquare(n^2\b) & print1(n^2, ", ")) CROSSREFS Sequence in context: A226076 A272711 A018228 * A138858 A076967 A233247 Adjacent sequences:  A204500 A204501 A204502 * A204504 A204505 A204506 KEYWORD nonn,base AUTHOR M. F. Hasler, Jan 15 2012 STATUS approved

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Last modified October 16 11:41 EDT 2019. Contains 328056 sequences. (Running on oeis4.)