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%I #10 Dec 18 2015 11:25:35
%S 0,1,2,4,8,16,32,64,129,259,519,1036,2074,4150,8296,16600,33208,66424,
%T 132832,265696,531424,1062880,2125696,4251521,8502785,17005825,
%U 34011905,68023301,136047622,272093206,544188470,1088378998,2176753882,4353515996,8707015520,17414063992,34828160840,69656354600,139312643368
%N Spironacci-style recurrence: a(0)=0, a(1)=1, a(n) = 2*a(n) XOR a(A265409(n)).
%C Spironacci-polynomials evaluated at X=2 over the field GF(2).
%C This is otherwise computed like A078510, which starts with a(0)=0 placed in the center of spiral (in square grid), followed by a(1) = 1, after which each term is a sum of two previous terms that are nearest when terms are arranged in a spiral, that is terms a(n-1) and a(A265409(n)), except here we first multiply the term a(n-1) by 2, and use carryless XOR (A003987) instead of normal addition.
%H Antti Karttunen, <a href="/A265407/b265407.txt">Table of n, a(n) for n = 0..256</a>
%F a(0)=0, a(1)=1; after which, a(n) = 2*a(n) XOR a(A265409(n)).
%F a(n) = A248663(A265408(n)).
%o (Scheme, with memoization-macro definec)
%o (definec (A265407 n) (if (< n 2) n (A003987bi (* 2 (A265407 (- n 1))) (A265407 (A265409 n)))))
%o ;; Where A003987bi computes bitwise-XOR as in A003987.
%Y Cf. A003987, A248663, A265408, A265409.
%Y Cf. also A078510, A264977.
%K nonn
%O 0,3
%A _Antti Karttunen_, Dec 13 2015
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