A063249 Doubly hexagonal numbers.
0, 1, 66, 435, 1540, 4005, 8646, 16471, 28680, 46665, 72010, 106491, 152076, 210925, 285390, 378015, 491536, 628881, 793170, 987715, 1216020, 1481781, 1788886, 2141415, 2543640, 3000025, 3515226, 4094091, 4741660, 5463165
Offset: 0
Examples
a(2)=66 since 6 is the 2nd hexagonal number and 66 is the 6th hexagonal number.
Links
- William A. Tedeschi, Table of n, a(n) for n = 0..10000
- Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).
Crossrefs
Programs
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Mathematica
LinearRecurrence[{5,-10,10,-5,1},{0,1,66,435,1540},30] (* Harvey P. Dale, Dec 02 2016 *)
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PARI
concat(0, Vec(-x*(15*x^3+115*x^2+61*x+1)/(x-1)^5 + O(x^100))) \\ Colin Barker, Sep 14 2014
Formula
G.f.: -x*(15*x^3+115*x^2+61*x+1) / (x-1)^5. - Colin Barker, Sep 14 2014