|
| |
|
|
A051201
|
|
Sum of elements of the set { [ n/k ] : 1 <= k <= n }.
|
|
7
| |
|
|
1, 3, 4, 7, 8, 12, 13, 15, 19, 21, 22, 28, 29, 31, 33, 39, 40, 43, 44, 51, 53, 55, 56, 60, 66, 68, 70, 73, 74, 83, 84, 87, 89, 91, 93, 103, 104, 106, 108, 112, 113, 123, 124, 127, 130, 132, 133, 138, 146, 149, 151, 154, 155, 159, 161, 172, 174, 176, 177, 183, 184, 186
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
FORMULA
| a(n) = m*(m+1)/2 + sum_{k=1..floor(n/(m+1))} floor(n/k), where m is the largest number such that m*(m+1) <= n, i.e., m=floor( (sqrt(4*n+1)-1)/2 ). [From Max Alekseyev (maxale(AT)gmail.com), Feb 12 2012]
|
|
|
PROG
| (PARI) { a(n) = m=(sqrtint(4*n+1)-1)\2; m*(m+1)/2 + sum(k=1, n\(m+1), n\k) } \\ From Max Alekseyev
|
|
|
CROSSREFS
| Cf. A006218
Sequence in context: A014602 A078823 A045615 * A026449 A165157 A129819
Adjacent sequences: A051198 A051199 A051200 * A051202 A051203 A051204
|
|
|
KEYWORD
| nonn,changed
|
|
|
AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
|
| |
|
|
