A105076 Numbers k such that 60*k^2 + 60*k + 1 is a square.
0, 1, 2, 11, 19, 90, 153, 712, 1208, 5609, 9514, 44163, 74907, 347698, 589745, 2737424, 4643056, 21551697, 36554706, 169676155, 287794595, 1335857546, 2265802057, 10517184216, 17838621864, 82801616185, 140443172858, 651895745267
Offset: 1
Keywords
Formula
From R. J. Mathar, Nov 13 2009: (Start)
a(n) = a(n-1) + 8*a(n-2) - 8*a(n-3) - a(n-4) + a(n-5).
G.f.: x^2*(1+x+x^2)/((1-x)*(x^4-8*x^2+1)). (End)
Extensions
Partially edited by Jon E. Schoenfield, Oct 13 2019