%I #16 Jul 02 2023 18:47:09
%S 1,28,946,32131,1091503,37078966,1259593336,42789094453,1453569618061,
%T 49378577919616,1677418079648878,56982836130142231,
%U 1935739010345186971,65758143515606214778,2233841140520266115476,75884840634173441711401
%N Triangular numbers k such that 2*k-1 is also a triangular number.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (35, -35, 1).
%F G.f.: x*(1-7*x+x^2)/((1-x)*(1-34*x+x^2)).
%t CoefficientList[ Series[x*(1 - 7*x + x^2)/((1 - x)*(1 - 34*x + x^2)), {x, 0, 16}], x] (* _Robert G. Wilson v_, Sep 01 2004 *)
%Y Cf. A075528, A124174.
%K easy,nonn
%O 1,2
%A _Vladeta Jovovic_, Aug 29 2004
%E More terms from _Robert G. Wilson v_, Sep 01 2004