Ljunggren, Wilhelm Zur Theorie der Gleichung \(x^2+1=Dy^4\). (German) Zbl 0027.01103 Avh. Norske Vid. Akad. Oslo 1942, No. 5, 1-27 (1942). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page Cited in 9 ReviewsCited in 21 Documents Keywords:Number fields, function fields PDFBibTeX XML Online Encyclopedia of Integer Sequences: Numbers k such that 2*k^2 - 1 is a square. Stella octangula numbers: a(n) = n*(2*n^2 - 1). Positive integer solutions y1, x1, y2, x2 to Ljunggren’s equation x^2 + 1 = 2y^4. Numbers n such that n^2 + 1 is 13-smooth.