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Search: a116626 -id:a116626
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Least natural number which does not occur in A116626(1..n).
+20
5
2, 2, 4, 4, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7, 9, 9, 11, 11, 11, 11, 11, 11, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21, 27, 27, 27, 27, 27, 27, 27, 27, 29, 29, 29, 29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 39, 39, 39, 39, 42, 42, 42, 42, 44, 44, 44, 44
OFFSET
1,1
PROG
(MIT Scheme:) (define (A116648 n) (if (< n 2) (+ n 1) (let ((prev (A116648 (- n 1)))) (cond ((not (= (A116626 n) prev)) prev) (else (let loop ((i (+ 1 prev))) (cond ((> (A116627 i) n) i) (else (loop (+ 1 i))))))))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 21 2006
STATUS
approved
a(n) = First integer i such that A116626(i) = n, 0 if n never occurs in A116626.
+20
2
1, 3, 2, 5, 9, 4, 15, 7, 17, 11, 23, 6, 8, 16, 10, 13, 19, 25, 29, 33, 41, 37, 14, 18, 24, 12, 49, 45, 53, 63, 57, 21, 27, 35, 31, 47, 59, 55, 67, 39, 43, 71, 22, 75, 79, 85, 89, 30, 20, 28, 26, 36, 44, 34, 32, 46, 56, 58, 54, 42, 40, 38, 48, 51, 61, 65, 73, 69, 81, 77, 95, 87
OFFSET
1,2
COMMENTS
If A116626 is really a permutation of natural numbers, then this is as well and no zeros are needed.
CROSSREFS
Inverse: A116626.
KEYWORD
nonn
AUTHOR
STATUS
approved
a(1)=1; for n>1, a(n) = least positive integer not appearing earlier such that {a(k) | 1 <= k <= n} and {a(k) XOR a(k-1) | 1 <= k <= n} are disjoint sets of distinct numbers.
+10
5
1, 2, 4, 8, 5, 10, 16, 7, 9, 17, 32, 11, 18, 33, 19, 35, 20, 34, 22, 40, 21, 41, 28, 36, 27, 64, 29, 38, 31, 37, 65, 30, 66, 39, 68, 42, 67, 44, 70, 45, 69, 128, 46, 72, 47, 77, 129, 71, 131, 73, 130, 74, 132, 75, 134, 79, 136, 80, 133, 81, 135, 84, 137, 82, 139, 85
OFFSET
1,2
COMMENTS
Another way to define this: A116624(1) = 1; A116624(n) = the least positive integer i distinct from any of A116624(1..n-1) and A116625(1..n-2), such that also (i XOR A116624(n-1)) is not present in A116625(1..n-2) nor in A116624(1..n-1).
LINKS
MATHEMATICA
a = {1}; used = {}; Do[k = 1; While[MemberQ[Join[a, used], k] || MemberQ[Join[a, used], r = BitXor[a[[-1]], k]], k++]; AppendTo[a, k]; AppendTo[used, r], {n, 2, 66}]; a (* Ivan Neretin, Mar 13 2017 *)
PROG
(MIT/GNU Scheme)
(define (A116624 n) (cond ((= 1 n) 1) (else (let outloop ((i 1)) (let ((k (A003987bi i (A116624 (- n 1))))) (let inloop ((j (- n 1))) (cond ((zero? j) i) ((= i (A116624 j)) (outloop (+ i 1))) ((= i (A116625 (- j 1))) (outloop (+ i 1))) ((= k (A116625 (- j 1))) (outloop (+ i 1))) ((= k (A116624 j)) (outloop (+ i 1))) (else (inloop (- j 1))))))))))
CROSSREFS
Cf. Bisection of A116626. Complement of A116625?
KEYWORD
nonn
AUTHOR
STATUS
approved
a(n) = A116624(n) XOR A116624(n+1).
+10
4
3, 6, 12, 13, 15, 26, 23, 14, 24, 49, 43, 25, 51, 50, 48, 55, 54, 52, 62, 61, 60, 53, 56, 63, 91, 93, 59, 57, 58, 100, 95, 92, 101, 99, 110, 105, 111, 106, 107, 104, 197, 174, 102, 103, 98, 204, 198, 196, 202, 203, 200, 206, 207, 205, 201, 199, 216, 213, 212
OFFSET
1,1
COMMENTS
XOR is A003987.
LINKS
CROSSREFS
Bisection of A116626. Complement of A116624?.
Cf. A235262.
KEYWORD
nonn
AUTHOR
STATUS
approved
Positions where A116648(i) is greater than A116648(i-1).
+10
2
1, 3, 5, 9, 15, 17, 23, 25, 29, 33, 41, 49, 53, 63, 67, 71, 75, 79, 85, 89, 95, 99, 103, 107, 139, 143, 163, 167, 175, 179, 199, 219, 223, 227, 235, 243, 267, 271, 275, 279, 283, 291, 299, 307, 323, 333, 337, 351, 357, 361, 371, 381, 395, 405, 425, 449, 457
OFFSET
1,2
COMMENTS
Equivalently, from i>1 onward those i where A116626(i) = A116648(i-1). Conjecture: all the terms are odd.
CROSSREFS
Cf. A116650.
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 21 2006
STATUS
approved

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