A180425 Number of positive integers below 10^n requiring 3 positive squares in their representation as sum of squares.

2, 42, 505, 5586, 59308, 616995, 6347878, 64875490, 660104281, 6695709182, 67762820595, 684596704482, 6907026402474, 69611115440126, 700946070114283, 7053023642205904

Offset: 1

Author

Martin Renner, Jan 19 2011

Keywords

• nonn
• more

Links

• Eric W. Weisstein, MathWorld -- Lagrange's Four-Square Theorem.
• Eric W. Weisstein, MathWorld -- Sum of Squares Function.

Crossrefs

Cf. A000419, A049416, A180416, A167615, A002283.

Formula

a(n) = #{k: A000419(k) < 10^n}.

A049416(n) + A180416(n) + a(n) + A167615(n) = A002283(n).

Extensions

a(6)=616995 by Lars Blomberg, May 03 2011

a(7)-a(10) from Donovan Johnson, Jul 01 2011

a(10) corrected and a(11)-a(16) from Hiroaki Yamanouchi, Jul 13 2014