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Triangular numbers k such that 2*k-1 is also a triangular number.
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%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