A183863 - OEIS

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A183863

n-1+ceiling((2/5)(-1/2+n^2)); complement of A183862.

1, 3, 6, 10, 14, 20, 26, 33, 41, 49, 59, 69, 80, 92, 104, 118, 132, 147, 163, 179, 197, 215, 234, 254, 274, 296, 318, 341, 365, 389, 415, 441, 468, 496, 524, 554, 584, 615, 647, 679, 713, 747, 782, 818, 854, 892, 930, 969, 1009, 1049, 1091, 1133, 1176, 1220, 1264, 1310, 1356, 1403, 1451, 1499, 1549, 1599, 1650, 1702, 1754, 1808, 1862, 1917, 1973, 2029

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

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..70.

Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,1,-2,1).

FORMULA

a(n)=n-1+ceiling((2/5)(-1/2+n^2)).

MATHEMATICA

a=5/2; b=1/2;

Table[n+Floor[(a*n+b)^(1/2)], {n, 80}]

Table[n-1+Ceiling[(n*n-b)/a], {n, 70}]