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 A015221 Odd square pyramidal numbers. 1
 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 Index entries for 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: A284066 A244439 A216446 * A035305 A057722 A078216 Adjacent sequences:  A015218 A015219 A015220 * A015222 A015223 A015224 KEYWORD nonn,easy AUTHOR EXTENSIONS More terms from Erich Friedman. STATUS approved

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