OFFSET
1,1
COMMENTS
For the first of the corresponding seven consecutive positive integers, see A262063.
LINKS
Colin Barker, Table of n, a(n) for n = 1..706
Index entries for linear recurrences with constant coefficients, signature (27,-27,1).
FORMULA
a(n) = 27*a(n-1)-27*a(n-2)+a(n-3) for n>3.
G.f.: -x*(x^2-26*x+85) / ((x-1)*(x^2-26*x+1)).
EXAMPLE
85 is in the sequence because 85^2 + ... + 90^2 = 45955 = 78^2 + ... + 84^2.
MATHEMATICA
CoefficientList[Series[(x^2 - 26 x + 85)/((1 - x) (x^2 - 26 x + 1)), {x, 0, 20}], x] (* Vincenzo Librandi, Sep 10 2015 *)
PROG
(PARI) Vec(-x*(x^2-26*x+85)/((x-1)*(x^2-26*x+1)) + O(x^20))
(Magma) I:=[85, 2269, 58969]; [n le 3 select I[n] else 27*Self(n-1)-27*Self(n-2)+Self(n-3): n in [1..20]]; // Vincenzo Librandi, Sep 10 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Sep 09 2015
STATUS
approved