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A183220 Complement of the octagonal numbers. 3
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 (list; graph; refs; listen; history; text; internal format)
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: A096432 A138302 A270428 * A187947 A242094 A171524

Adjacent sequences:  A183217 A183218 A183219 * A183221 A183222 A183223

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 01 2011

STATUS

approved

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Last modified May 12 19:15 EDT 2021. Contains 343829 sequences. (Running on oeis4.)