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%I M3348 #37 Aug 06 2021 05:33:10
%S 0,1,4,9,1,2,3,4,6,8,1,1,1,1,1,2,2,2,3,3,4,4,4,5,5,6,6,7,7,8,9,9,1,1,
%T 1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,4,4,4,4,
%U 4,4,4,5,5,5,5,5,5,5,6,6,6,6,6,6,7,7,7,7,7,7,8,8,8,8,8,9,9,9,9,9,1
%N Initial digits of squares.
%C a(n) = A000030(A000290(n)). - _Reinhard Zumkeller_, Aug 17 2008
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H T. D. Noe, <a href="/A002993/b002993.txt">Table of n, a(n) for n = 0..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GelfandsQuestion.html">Gelfand's Question</a>
%p a:= n-> parse(""||(n^2)[1]):
%p seq(a(n), n=0..100); # _Alois P. Heinz_, Aug 06 2021
%t a[n_] := First[IntegerDigits[n^2]]; Table[a[n], {n, 0, 100} (* _Vladimir Joseph Stephan Orlovsky_, Dec 21 2008 *)
%t First[IntegerDigits[#]]&/@(Range[70]^2) (* _Harvey P. Dale_, Feb 09 2011 *)
%o (Haskell)
%o a002993 = a000030 . a000290 -- _Reinhard Zumkeller_, Apr 01 2015
%Y Cf. A000030, A000290, A089951, A002994.
%K nonn,base
%O 0,3
%A _N. J. A. Sloane_
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