A183219 - OEIS

A183219

Complement of the heptagonal (7-gonal) numbers.

2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

FORMULA

n+Floor[1/2+(2n/5)^(1/2)].

EXAMPLE

7-gonal numbers: (1,7,18,34,55,...)=A000566, so that

A183219=(2,3,4,5,6,8,9,...17,19,...33,35,...).

MATHEMATICA

Table[n+Floor[1/2+(2n/5)^(1/2)], {n, 100}]