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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.

%I A055859 #18 Aug 03 2017 00:15:16
%S A055859 0,1,4,9,64,256,2025,16129,64516,514089,4096576,16386304,130576329,
%T A055859 1040514049,4162056196,33165873225,264286471744,1057145886976,
%U A055859 8424001222569,67127723308801,268510893235204,2139663144659049,17050177433963584,68200709735854336
%N 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.
%C A055859 Square roots of a(n) are listed in A204516, square roots of floor(a(n)/7) in A204517. - _M. F. Hasler_, Jan 16 2012
%H A055859 M. F. Hasler, <a href="/wiki/M. F. Hasler/Truncated_squares">Truncated squares</a>, OEIS wiki, Jan 16 2012
%H A055859 <a href="/index/Sq#sqtrunc">Index to sequences related to truncating digits of squares</a>.
%F A055859 a(n) = A204516(n)^2. - _M. F. Hasler_, Jan 16 2012
%F A055859 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
%e A055859 a(5) = 256 because 256 = 16^2 = 514 base 7 and 51 base 7 = 36 = 6^2.
%Y A055859 Cf. A023110.
%K A055859 base,nonn
%O A055859 1,3
%A A055859 _Henry Bottomley_, Jul 14 2000