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A257954
Heptagonal numbers (A000566) that are the sum of seven consecutive heptagonal numbers.
2
380300389, 13416840252277, 102114787991863121805337, 3602567760523753992917728705, 27418932936218445934971843788960252365, 967328687318574474761362987583880892300813, 7362282174260114825535960626325353709734456640627073
OFFSET
1,1
LINKS
Index entries for linear recurrences with constant coefficients, signature (1, 268510893235202, -268510893235202, -1, 1).
FORMULA
a(n) = a(n-1)+268510893235202*a(n-2)-268510893235202*a(n-3)-a(n-4)+a(n-5).
G.f.: -7*x*(847*x^4 +29708856*x^3 -1309948358220074*x^2 +1916637135984*x +54328627) / ((x -1)*(x^2 -16386302*x +1)*(x^2 +16386302*x +1)).
EXAMPLE
380300389 is in the sequence because H(12334) = 380300389 = 54258714 + 54282010 + 54305311 + 54328617 + 54351928 + 54375244 + 54398565 = H(4659)+...+H(4665).
PROG
(PARI) Vec(-7*x*(847*x^4 +29708856*x^3 -1309948358220074*x^2 +1916637135984*x +54328627) / ((x -1)*(x^2 -16386302*x +1)*(x^2 +16386302*x +1)) + O(x^20))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, May 14 2015
STATUS
approved