1,2

Also, odd square-triangular numbers (or bisection of A001110 = {0, 1, 36, 1225, 41616, 1413721, 48024900, 1631432881, ...} = Numbers that are both triangular and square: a(n) = 34a(n-1) - a(n-2) + 2). - Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 06 2007

Let be y^2=x*(2*x-1)=H_x (x>=1). The least both hexagonal and square number which is greater than y^2 is given by the relation (24*x+17*y-6)^2 = H_{17*x+12*y-4}. [From Richard Choulet (richardchoulet(AT)yahoo.fr), May 01 2009]

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Eric Weisstein, Link to a section of The World of Mathematics. Square Triangular Number.

a(n) = A001110(2n-1). - Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 06 2007

a(n+1)=577*a(n)+36+204*(8*a(n)^2+a(n))^0.5 for n>=1 (a(0)=1) [From Richard Choulet (richardchoulet(AT)yahoo.fr), May 01 2009]

a(n+2)=1154*a(n+1)-a(n)+72 for n>=0. [From Richard Choulet (richardchoulet(AT)yahoo.fr), May 01 2009]

Cf. A008844, A046176.

Cf. A001110 = Numbers that are both triangular and square: a(n) = 34a(n-1) - a(n-2) + 2.

Adjacent sequences: A046174 A046175 A046176 this_sequence A046178 A046179 A046180

Sequence in context: A025405 A014795 A151657 this_sequence A031748 A031623 A031533

nonn

Eric Weisstein (eric(AT)weisstein.com)