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A167047 Angry numbers: each number n must be more than n places from n-1 and n+1. This sequence makes each number as small as possible as it occurs. 1
1, 3, 5, 7, 9, 2, 11, 13, 4, 15, 17, 6, 19, 21, 8, 23, 25, 27, 10, 29, 31, 12, 33, 35, 37, 14, 39, 41, 16, 43, 45, 47, 18, 49, 51, 20, 53, 55, 57, 22, 59, 61, 24, 63, 65, 26, 67, 69, 71, 28, 73, 75, 30, 77, 79, 81, 32, 83, 85, 34, 87, 89, 36, 91, 93, 95, 38, 97, 99, 40, 101, 103 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
This sequence is a permutation of the positive integers. A number cannot remain unassigned indefinitely; eventually the placement gets far enough from its neighbors and it gets used.
Each term in this sequence is either the next unused even number or the next unused odd number; after the initial 5 terms there are always 2 or 3 odd numbers between each pair of even numbers.
LINKS
EXAMPLE
After a(1) = 1, we cannot have a(2) = 2, because then 1 and 2 would be too close. a(2) = 3 is OK. Now a(3) can't be 2 because then 2 and 3 would be too close; 4 would also be too close to 3, but 5 is OK. Skipping ahead, a(6) is the first place where 2 is not too close to 3, so a(6) = 2.
PROG
(PARI) dist(n) = n+1
al(n)= {local(v, w, mn, ok);
v=vector(n); w=vector(2*n); u=vector(n);
v[1]=w[1]=1; mn=2;
for(k=2, n,
j=mn-1; ok=0;
while(!ok,
j++; ok=w[j]==0;
if(ok&w[j-1]&abs(k-w[j-1])<dist(j), ok=0);
if(ok&w[j+1]&abs(k-w[j+1])<dist(j+1), ok=0));
v[k]=j; w[j]=k);
while(w[mn], mn++);
v}
CROSSREFS
Sequence in context: A131669 A004155 A163125 * A065271 A213542 A029657
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified June 25 10:15 EDT 2024. Contains 373701 sequences. (Running on oeis4.)