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A015221 Odd square pyramidal numbers. 0
1, 5, 55, 91, 285, 385, 819, 1015, 1785, 2109, 3311, 3795, 5525, 6201, 8555, 9455, 12529, 13685, 17575, 19019, 23821, 25585, 31395, 33511, 40425, 42925, 51039, 53955, 63365, 66729, 77531, 81375, 93665, 98021, 111895, 116795, 132349, 137825 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..37.

Index to sequences with linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1)

FORMULA

Odd numbers in A000330.

Contribution from Ant King, Oct 17 2012: (Start)

a(n) = 3*a(n-2)-3*a(n-4)+a(n-6)+128.

a(n) = 1/24*(1+4*n+(-1)^n)*(2+4*n+(-1)^n)*(3+4*n+(-1)^n).

G. f. (1+4*x+47*x^2+24*x^3+47*x^4+4*x^5+x^6)/((1-x)^4*(1+x)^3).

(End)

MATHEMATICA

LinearRecurrence[{1, 3, -3, -3, 3, 1, -1}, {1, 5, 55, 91, 285, 385, 819}, 38] (* Ant King Oct 17 2012 *)

CROSSREFS

Sequence in context: A247711 A244439 A216446 * A035305 A057722 A078216

Adjacent sequences:  A015218 A015219 A015220 * A015222 A015223 A015224

KEYWORD

nonn,easy

AUTHOR

Mohammad K. Azarian

EXTENSIONS

More terms from Erich Friedman.

STATUS

approved

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Last modified December 18 06:31 EST 2014. Contains 252079 sequences.