A217976 First time n appears in the first differences of n*log(n): A217865.

1, 2, 4, 9, 21, 62, 159, 422, 1134, 3056, 8139, 22169, 60004, 163262, 443002

Offset

1,2

Comments

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

For example the last time 5 appears is at position 135, the first time 7 appears is at position 159.

Links

Table of n, a(n) for n=1..15.

Prog

(JavaScript)
function firstIndex(arr, k) {
p=-1;
for (a=1; a<arr.length; a++) if (arr[a]==k) {p=a; return p; }
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(firstIndex(d, i)+", ");

Crossrefs

Cf. A217866.

Sequence in context: A351364 A058718 A148076 * A156801 A363771 A057580

Adjacent sequences: A217973 A217974 A217975 * A217977 A217978 A217979

Keyword

nonn

Author

Jon Perry, Oct 16 2012

Status

approved