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A183221 Complement of the 9-gonal numbers. 1
2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105 (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+(2n/7)^(1/2)].

MATHEMATICA

Table[n+Floor[1/2+(2n/7)^(1/2)], {n, 100}]

CROSSREFS

Cf. A001106 (9-gonal numbers).

Sequence in context: A004728 A072886 A031980 * A317492 A324721 A327534

Adjacent sequences:  A183218 A183219 A183220 * A183222 A183223 A183224

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 01 2011

STATUS

approved

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Last modified November 14 22:17 EST 2019. Contains 329134 sequences. (Running on oeis4.)