OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..588
Index entries for linear recurrences with constant coefficients, signature (51,-51,1).
FORMULA
a(n) = 51*a(n-1)-51*a(n-2)+a(n-3) for n>3.
G.f.: 26*x*(3*x^2-50*x-1) / ((x-1)*(x^2-50*x+1)).
a(n) = 26*(-6-(6+sqrt(39))*(25+4*sqrt(39))^(-n)+(-6+sqrt(39))*(25+4*sqrt(39))^n)/6. - Colin Barker, Mar 03 2016
EXAMPLE
26 is in the sequence because (26+52)^3 - 26^3 = 676^2.
MATHEMATICA
LinearRecurrence[{51, -51, 1}, {26, 2626, 132522}, 20] (* Harvey P. Dale, Feb 05 2019 *)
PROG
(PARI) Vec(26*x*(3*x^2-50*x-1)/((x-1)*(x^2-50*x+1)) + O(x^30))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Oct 30 2015
STATUS
approved