OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..416
Index entries for linear recurrences with constant coefficients, signature (1,64514,-64514,-1,1).
FORMULA
a(n) = a(n-1)+64514*a(n-2)-64514*a(n-3)-a(n-4)+a(n-5).
G.f.: -x*(x^4+840*x^3-21842*x^2+840*x+1) / ((x-1)*(x^2-254*x+1)*(x^2+254*x+1)).
EXAMPLE
841 is in the sequence because it is the 21st centered square number and the 16th centered heptagonal number.
MATHEMATICA
LinearRecurrence[{1, 64514, -64514, -1, 1}, {1, 841, 43513, 54236113, 2807177521}, 20] (* Harvey P. Dale, Mar 26 2023 *)
PROG
(PARI) Vec(-x*(x^4+840*x^3-21842*x^2+840*x+1)/((x-1)*(x^2-254*x+1)*(x^2+254*x+1)) + O(x^100))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jan 05 2015
STATUS
approved