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A183857 a(n) = n - 1 + ceiling((2/3)*n^2); complement of A183874. 1
1, 4, 8, 14, 21, 29, 39, 50, 62, 76, 91, 107, 125, 144, 164, 186, 209, 233, 259, 286, 314, 344, 375, 407, 441, 476, 512, 550, 589, 629, 671, 714, 758, 804, 851, 899, 949, 1000, 1052, 1106, 1161, 1217, 1275, 1334, 1394, 1456, 1519, 1583, 1649, 1716, 1784, 1854, 1925, 1997, 2071 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..55.

Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).

FORMULA

a(n) = n - 1 + ceiling((2/3)n^2).

MATHEMATICA

a=3/2; b=0;

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

Table[n-1+Ceiling[(n*n-b)/a], {n, 80}]

LinearRecurrence[{2, -1, 1, -2, 1}, {1, 4, 8, 14, 21}, 60] (* Harvey P. Dale, Apr 12 2020 *)

CROSSREFS

Cf. A183874.

Sequence in context: A312698 A312699 A131937 * A088804 A344012 A027924

Adjacent sequences:  A183854 A183855 A183856 * A183858 A183859 A183860

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jan 07 2011

STATUS

approved

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Last modified July 25 13:59 EDT 2021. Contains 346290 sequences. (Running on oeis4.)