A225206 Number of Pythagorean quadruples (a, b, c, d) with d < 10^n.

6, 571, 56268, 5614390, 561232920, 56120665334, 5612026652893, 561202243017532, 56120219419339591

Offset: 1

Author

Arkadiusz Wesolowski, May 01 2013

Keywords

• more
• nonn

Comments

a(n) ~ Pi*A225207(n)/(1+G), where G is Catalan's constant (A006752).

Examples

			a(1) = 6 because there are six solutions (a, b, c, d) as follows: (1, 2, 2, 3), (2, 4, 4, 6), (2, 3, 6, 7), (1, 4, 8, 9), (3, 6, 6, 9), (4, 4, 7, 9) with d < 10.
		

Links

• Wikipedia, Pythagorean quadruple

Crossrefs

Cf. A169580, A181786, A225207.

Formula

a(n) = Sum_{k=1..10^n-1} A181786(k). - Max Alekseyev, Feb 28 2023

Extensions

a(4) from Giovanni Resta, May 01 2013

a(5)-a(9) from Max Alekseyev, Feb 28 2023