A183223 Complement of the 11-gonal numbers.

2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 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, 96, 97, 98, 99, 100, 101, 102

Offset: 1

Author

Clark Kimberling, Jan 01 2011

Keywords

• nonn

Crossrefs

Cf. A051682 (11-gonal numbers).

Programs

Mathematica

 Table[n+Floor[1/2+(2n/9+2/9)^(1/2)], {n,100}]

Python

from math import isqrt
def A183223(n): return n+(isqrt((n<<3|4)//9)+1>>1) # Chai Wah Wu, Oct 06 2024

Formula

a(n) = n + floor(1/2+(2n/9+2/9)^(1/2)).