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 A088126 Let f(n, x) = x+3x^2+6x^3+...+(n(n+1)/2)x^n; then a(n) = least x such that f(n, x) is a triangular number, or 0 if no such x exists. 1

%I

%S 1,18,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,

%T 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

%N Let f(n, x) = x+3x^2+6x^3+...+(n(n+1)/2)x^n; then a(n) = least x such that f(n, x) is a triangular number, or 0 if no such x exists.

%C If k is a member of A027568 (both triangular and tetrahedral) then k = A000292(n-1) for some n and a(n) = 1.

%C Zero values are conjectures. I have searched for a(4) up to x = 10^7, a(5) up to x = 10^6 and the rest up to x = 10^4. (Wasserman)

%Y Cf. A087702.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Sep 26 2003

%E Edited and extended by _David Wasserman_, Jun 16 2005

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Last modified December 6 21:48 EST 2019. Contains 329809 sequences. (Running on oeis4.)