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A265407 Spironacci-style recurrence: a(0)=0, a(1)=1, a(n) = 2*a(n) XOR a(A265409(n)). 5
0, 1, 2, 4, 8, 16, 32, 64, 129, 259, 519, 1036, 2074, 4150, 8296, 16600, 33208, 66424, 132832, 265696, 531424, 1062880, 2125696, 4251521, 8502785, 17005825, 34011905, 68023301, 136047622, 272093206, 544188470, 1088378998, 2176753882, 4353515996, 8707015520, 17414063992, 34828160840, 69656354600, 139312643368 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Spironacci-polynomials evaluated at X=2 over the field GF(2).

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.

LINKS

Antti Karttunen, Table of n, a(n) for n = 0..256

FORMULA

a(0)=0, a(1)=1; after which, a(n) = 2*a(n) XOR a(A265409(n)).

a(n) = A248663(A265408(n)).

PROG

(Scheme, with memoization-macro definec)

(definec (A265407 n) (if (< n 2) n (A003987bi (* 2 (A265407 (- n 1))) (A265407 (A265409 n)))))

;; Where A003987bi computes bitwise-XOR as in A003987.

CROSSREFS

Cf. A003987, A248663, A265408, A265409.

Cf. also A078510, A264977.

Sequence in context: A079845 A278995 A117302 * A023422 A084638 A157021

Adjacent sequences:  A265404 A265405 A265406 * A265408 A265409 A265410

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 13 2015

STATUS

approved

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Last modified February 23 23:02 EST 2018. Contains 299595 sequences. (Running on oeis4.)