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 A055859 a(n) and floor(a(n)/7) are both squares; i.e., squares which remain squares when written in base 7 and last digit is removed. 15
 0, 1, 4, 9, 64, 256, 2025, 16129, 64516, 514089, 4096576, 16386304, 130576329, 1040514049, 4162056196, 33165873225, 264286471744, 1057145886976, 8424001222569, 67127723308801, 268510893235204, 2139663144659049, 17050177433963584, 68200709735854336 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Square roots of a(n) are listed in A204516, square roots of floor(a(n)/7) in A204517. - M. F. Hasler, Jan 16 2012 LINKS M. F. Hasler, Truncated squares, OEIS wiki, Jan 16 2012 FORMULA a(n) = A204516(n)^2. - M. F. Hasler, Jan 16 2012 Empirical g.f.: -x^2*(9*x^8+256*x^7+64*x^6-270*x^5-764*x^4-191*x^3+9*x^2+4*x+1) / ((x-1)*(x^2+x+1)*(x^6-254*x^3+1)). - Colin Barker, Sep 15 2014 EXAMPLE a(5) = 256 because 256 = 16^2 = 514 base 7 and 51 base 7 = 36 = 6^2. CROSSREFS Cf. A023110. Sequence in context: A095175 A092396 A184877 * A162991 A062926 A069020 Adjacent sequences:  A055856 A055857 A055858 * A055860 A055861 A055862 KEYWORD base,nonn AUTHOR Henry Bottomley, Jul 14 2000 STATUS approved

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Last modified April 3 04:21 EDT 2020. Contains 333195 sequences. (Running on oeis4.)