OFFSET
1,2
COMMENTS
Row n begins with the number of divisors of n and ends with 2n-1. Observe that the reverse of row n starts 2n-1, 2n-2, 2n-4, 2n-5,...; that is, 2n-r where r is in A001651, numbers not divisible by 3. Why?
LINKS
T. D. Noe, Rows n=1..100, flattened
EXAMPLE
For n=5, we have 2 numbers that divide 5 (namely, 1 and 5), 5 numbers that divide numbers in the range [5,6] (namely, 1, 2, 3, 5 and 6), 6 divisors that divide numbers in the range [5,7] (namely, 1, 2, 3, 5, 6 and 7), 8 divisors that divide numbers in the range [5,8] (namely, all numbers from 1 to 8), and 9 divisors that divide numbers in the range [5,9] (namely, all numbers from 1 to 9). Hence row 5 is 2, 5, 6, 8, 9.
MATHEMATICA
Flatten[Table[Length[Union[Flatten[Divisors[Range[n, n+k]]]]], {n, 50}, {k, 0, n-1}]]
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
T. D. Noe, Feb 06 2010
STATUS
approved