A258204 Number of one-sided strictly non-overlapping holeless polyhexes of perimeter 2n, counted up to rotation.

0, 0, 1, 0, 1, 1, 3, 3, 16, 23, 80, 183, 563

Offset

1,7

Comments

For n >= 1, a(n) gives the total number of terms k in A258003 with binary width = 2n + 1, or equally, with A000523(k) = 2n.

Links

Table of n, a(n) for n=1..13.

Formula

Other identities and observations. For all n >= 1:

a(n) = 2*A258206(n) - A258205(n).

a(n) <= A258017(n).

Prog

(Scheme)
(define (A258204 n) (let loop ((k (+ 1 (expt 2 (+ n n)))) (c 0)) (cond ((pow2? k) c) (else (loop (+ 1 k) (+ c (if (isA258003? k) 1 0)))))))
(define (pow2? n) (let loop ((n n) (i 0)) (cond ((zero? n) #f) ((odd? n) (and (= 1 n) i)) (else (loop (/ n 2) (1+ i)))))) ;; Gives non-false only when n is a power of two.
;; Code for isA258003? given in A258003.

Crossrefs

Cf. A057779, A258003, A258017, A258205, A258206.

Sequence in context: A292356 A370869 A209020 * A258017 A209055 A209212

Adjacent sequences: A258201 A258202 A258203 * A258205 A258206 A258207

Keyword

nonn,more

Author

Antti Karttunen, May 31 2015

Status

approved