A217866 Last time n appears in the first differences of n*log(n): A217865.

1, 5, 18, 46, 137, 384, 1059, 2905, 8066, 21883, 59743, 162247, 441824

Offset

1,2

Comments

Conjecture: the last time n appears is always before the first time n+2 appears.

For example, examine: 1, 2, 2, 3, 2, 3, 3, 3, 4, 3, 3, 4, 3, 4, 4, 4, 4, 3, 4, 4, 5, 4, 4, 4 (A217865).

We can see that the last 2 is before the first 4, the last 3 is before the first 5, etc.

Links

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

Example

2 lasts appears in A217865 at position 5 so a(2)=5.

Prog

(JavaScript)
function lastIndex(arr, k) {
p=-1;
for (a=1; a<arr.length; a++) if (arr[a]==k) p=a;
return p;
}
d=new Array();
for (i=1; i<500000; i++)
d[i]=Math.floor((i+1)*Math.log(i+1))-Math.floor(i*Math.log(i));
for (i=1; i<100; i++) document.write(lastIndex(d, i)+", ");

Crossrefs

Cf. A217865.

Cf. A217976.

Sequence in context: A273559 A272792 A273566 * A256539 A109363 A218214

Adjacent sequences: A217863 A217864 A217865 * A217867 A217868 A217869

Keyword

nonn

Author

Jon Perry, Oct 13 2012

Status

approved