A023112 Squares that remain square when the digit 4 is appended.

0, 144, 207936, 299843856, 432374632704, 623483920515600, 899063381008862784, 1296448771930859619216, 1869478230060918562046976, 2695786311299072635612120464, 3887321991415032679634115662400

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Comments

The terms of the sequence are the squares of the y-values in the solution to the Pellian equation x^2-10*y^2=4. - Colin Barker, Sep 28 2013

Formula

Empirical g.f.: -144*x^2*(x+1) / ((x-1)*(x^2-1442*x+1)). - Colin Barker, Jan 31 2013

a(n) = 4*A023111(n). - Colin Barker, Sep 28 2013