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A194073 a(n) = 1 + floor((3/4)*n^2). 4
1, 4, 7, 13, 19, 28, 37, 49, 61, 76, 91, 109, 127, 148, 169, 193, 217, 244, 271, 301, 331, 364, 397, 433, 469, 508, 547, 589, 631, 676, 721, 769, 817, 868, 919, 973, 1027, 1084, 1141, 1201, 1261, 1324, 1387, 1453, 1519, 1588, 1657, 1729, 1801 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..49.

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

FORMULA

a(n) = 1 + floor((3/4)*n^2).

G.f.: x*(1+2*x-x^2+x^3) / ( (1+x)*(1-x)^3 ). - R. J. Mathar, Aug 25 2011

a(n) = 1 + 3*A002620(n). - R. J. Mathar, Aug 25 2011

MATHEMATICA

c[k_]:=1+Floor[(3/4)k^2];

Table[c[k], {k, 1, 90}]

PROG

(PARI) a(n)=3*n^2\4+1 \\ Charles R Greathouse IV, Oct 16 2015

CROSSREFS

Cf. A194074 (natural fractal sequence of A194073),

A194075 (natural interspersion of A194074).

Sequence in context: A075315 A238327 A243811 * A023496 A191868 A176003

Adjacent sequences:  A194070 A194071 A194072 * A194074 A194075 A194076

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Aug 14 2011

STATUS

approved

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Last modified October 18 14:48 EDT 2019. Contains 328161 sequences. (Running on oeis4.)