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Natural function used for generating x^2 and sqrt(x) only using iteration and Q(x) (the characteristic function of sqrt).
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%I #3 May 08 2023 07:16:37

%S 0,3,4,5,8,9,10,11,12,15,16,17,18,19,20,21,24,25,26,27,28,29,30,31,32,

%T 35,36,37,38,39,40,41,42,43,44,45,48,49,50,51,52,53,54,55,56,57,58,59,

%U 60,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,80,81,82,83,84,85,86

%N Natural function used for generating x^2 and sqrt(x) only using iteration and Q(x) (the characteristic function of sqrt).

%C The sequence can be defined as follows: a(0) = 0, a(n+1) = b(a(n)) where b(n) = n + 2*Q(n+4) + 1 (Q is given in A010052)

%D R. M. Robinson, Primitive Recursive Functions, Bulletin of the American Mathematical Society, Vol. 53 (1947), pp. 925-942.

%F a(n) = n + 2*floor(sqrt(n)) = n+2*A000196(n).

%Y Cf. A010052.

%K nonn

%O 0,2

%A Daniel E. Severin (danielseverin(AT)yahoo.es), Dec 24 2005