A183217 Complement of the pentagonal numbers.

2, 3, 4, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 93

Offset

1,1

Links

Table of n, a(n) for n=1..85.

Formula

a(n)= n+Floor[1/2+(2n/3)^(1/2)].

Example

The pentagonal numbers:  A000326=(1,5,12,22,35,...), so that A183217=(2,3,4,6,7,8,9,10,11,13,14,...).

Mathematica

Table[n+Floor[1/2+(2n/3)^(1/2)], {n, 100}]

Crossrefs

Cf. A000326.

Sequence in context: A048263 A141451 A285211 * A047303 A057906 A039214

Adjacent sequences: A183214 A183215 A183216 * A183218 A183219 A183220

Keyword

nonn

Author

Clark Kimberling, Jan 01 2011

Status

approved