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

1,1

Links

Table of n, a(n) for n=1..16.

Eric W. Weisstein, MathWorld -- Lagrange's Four-Square Theorem.

Eric W. Weisstein, MathWorld -- Sum of Squares Function.

Formula

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

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

Crossrefs

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

Sequence in context: A070808 A229474 A157056 * A140170 A318247 A038396

Adjacent sequences: A180422 A180423 A180424 * A180426 A180427 A180428

Keyword

nonn,more

Author

Martin Renner, Jan 19 2011

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

Status

approved