A183220 Complement of the octagonal numbers.

2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106

Offset

1,1

Links

Table of n, a(n) for n=1..100.

Formula

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

Example

Octagonal numbers: (1,8,21,40,65,...), so that
A183220 = (2,3,4,5,6,7,9,10,...,20,22,...39,41...).

Mathematica

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

Crossrefs

Cf. A000567 (octagonal numbers).

Sequence in context: A369938 A138302 A270428 * A187947 A242094 A349144

Adjacent sequences: A183217 A183218 A183219 * A183221 A183222 A183223

Keyword

nonn

Author

Clark Kimberling, Jan 01 2011

Status

approved