A024388 [ (3rd elementary symmetric function of S(n))/(2nd elementary symmetric function of S(n)) ], where S(n) = {first n+2 positive integers congruent to 1 mod 4}.

3, 7, 12, 18, 26, 35, 46, 58, 71, 86, 101, 119, 137, 157, 178, 201, 225, 250, 276, 304, 334, 364, 396, 429, 464, 500, 537, 575, 615, 657, 699, 743, 788, 835, 883, 932, 982, 1034, 1088, 1142, 1198, 1255, 1314, 1374, 1435, 1497, 1561, 1627, 1693, 1761, 1830

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

Formula

Empirical g.f.: x*(x^20 -2*x^19 +x^18 +x^12 -2*x^11 +x^10 +x^9 -x^8 -x^7 -2*x^6 -x^5 -2*x^4 -x^3 -x^2 -x -3) / ((x -1)^3*(x^2 +x +1)*(x^6 +x^3 +1)). - Colin Barker, Aug 16 2014

a(n) = floor(A024379(n + 1) / A024378(n + 2)). - Sean A. Irvine, Jul 06 2019

Extensions

More terms from Joshua Zucker, May 20 2006