A135106 -id:A135106 - cp's OEIS frontend

A248837 Number of length n arrays x(i), i=1..n with x(i) in 0..i and no value appearing more than 3 times.

2, 6, 24, 118, 686, 4598, 34872, 295044, 2753958, 28103804, 311216626, 3716341042, 47597786154, 650812077852, 9461423560788, 145724617925326, 2370293673319292, 40600119927220706, 730458115445479734, 13772063820971722638

Offset: 1

R. H. Hardin, Oct 15 2014

nonn

Column 3 of A248842.

Essentially the same as A135106. - Georg Fischer, Oct 23 2018

			Some solutions for n=6
..0....1....0....1....0....0....1....1....1....0....0....0....0....0....0....1
..2....1....0....2....1....1....1....1....1....1....1....0....0....0....1....1
..2....0....0....0....1....1....2....2....0....3....0....2....3....3....2....2
..1....0....3....0....0....1....4....4....1....0....1....1....2....4....4....1
..5....0....2....2....3....4....5....2....2....4....4....0....1....0....5....5
..3....5....3....1....5....2....5....2....5....0....2....5....0....2....0....6

R. H. Hardin, Table of n, a(n) for n = 1..210

A204330 a(n) is the number of k satisfying 1 <= k <= n and such that floor(sqrt(k)) divides k.

Original entry on oeis.org

1, 2, 3, 4, 4, 5, 5, 6, 7, 7, 7, 8, 8, 8, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 15, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 18, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 21, 22, 22, 22, 22, 22, 22, 22

Offset: 1

Benoit Cloitre, Jan 14 2012

nonn

a(n) = floor(2*sqrt(n)) + floor(sqrt(n-1)) - 1 if n belongs to A135106 otherwise a(n) = floor(2*sqrt(n)) + floor(sqrt(n-1)) - 2.

B. Cloitre, Some divisibility sequences

Cf. A006446, A079631.

Accumulate[Boole[Table[IntegerQ[n/Floor[n^(1/2)]], {n, 1, 70}]]]  (* Geoffrey Critzer, May 25 2013 *)

PARI
```
a(n)=sum(k=1,n,if(k%sqrtint(k),0,1));
```

a(n) = card{j>=1, A006446(j)<=n}.

Corrected by Geoffrey Critzer, May 25 2013

cp's OEIS Frontend

A248837 Number of length n arrays x(i), i=1..n with x(i) in 0..i and no value appearing more than 3 times.

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A204330 a(n) is the number of k satisfying 1 <= k <= n and such that floor(sqrt(k)) divides k.

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