

A181106


Largest odd number strictly less than a square.


2



1, 3, 7, 15, 23, 35, 47, 63, 79, 99, 119, 143, 167, 195, 223, 255, 287, 323, 359, 399, 439, 483, 527, 575, 623, 675, 727, 783, 839, 899, 959, 1023, 1087, 1155, 1223, 1295, 1367, 1443, 1519, 1599, 1679, 1763, 1847, 1935, 2023, 2115, 2207, 2303, 2399, 2499
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OFFSET

1,2


COMMENTS

The terms are the negatives of A141354 and therefore have the same generating function except the sign.


LINKS

Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (2,0,2,1).


FORMULA

a(n) = n^2  2^(n mod 2) = A141354(n1).
From Colin Barker, Jun 27 2015: (Start)
a(n) = n^2  1 for n even; a(n) = n^2  2 for n odd.
a(n) = 2*a(n1)  2*a(n3) + a(n4).
G.f.: x*(x^3x^25*x+1) / ((x1)^3*(x+1)).
(End)


MATHEMATICA

Table[n^22^Mod[n, 2], {n, 50}] (* Ray Chandler, Dec 05 2011*)


PROG

(PARI) Vec(x*(x^3x^25*x+1)/((x1)^3*(x+1)) + O(x^100)) \\ Colin Barker, Jun 27 2015


CROSSREFS

Equals minus A141354.
Cf. A120413 (Largest even number strictly less than a square).
Sequence in context: A187220 A067317 A141354 * A131753 A171503 A283008
Adjacent sequences: A181103 A181104 A181105 * A181107 A181108 A181109


KEYWORD

easy,sign


AUTHOR

Jerzy Kocik (jkocik(AT)siu.edu), Oct 03 2010


EXTENSIONS

Edited by Ray Chandler, Dec 05 2011


STATUS

approved



