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Indices of the 7-gonal numbers that are the sum of 2 consecutive 7-gonal numbers.
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%I #11 Dec 07 2015 23:02:10

%S 1,241,19265,9435905,755214769,369906335809,29605929343313,

%T 14501068166936753,1160611641361329697,568470873910348243537,

%U 45498297535040917426721,22285195184532403676188961,1783624258808062403600975185,873624221055568415003611393825

%N Indices of the 7-gonal numbers that are the sum of 2 consecutive 7-gonal numbers.

%C Also nonnegative integers y in the solution to 10*x^2 - 5*y^2 + 4*x + 3*y + 2 = 0, the corresponding values of x being A133328.

%H Colin Barker, <a href="/A133327/b133327.txt">Table of n, a(n) for n = 1..436</a>

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,39202,-39202,-1,1).

%F The bisections modulo 2 satisfy the same recurrence relation: a(n+2) = 39202*a(n+1) - a(n) - 11760.

%F G.f.: -x*(17*x^4+8160*x^3-20178*x^2+240*x+1) / ((x-1)*(x^2-198*x+1)*(x^2+198*x+1)). - _Colin Barker_, Dec 05 2014

%o (PARI) Vec(-x*(17*x^4+8160*x^3-20178*x^2+240*x+1)/((x-1)*(x^2-198*x+1)*(x^2+198*x+1)) + O(x^100)) \\ _Colin Barker_, Dec 05 2014

%Y Cf. A133324, A133328.

%K nonn,easy

%O 1,2

%A _Richard Choulet_, Oct 18 2007

%E More terms from _Colin Barker_, Dec 05 2014