A152595 a(n) = the number of integers i in [1,n] that can be expressed as the sum of two squares of positive integers.

0, 1, 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 6, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 12, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 18, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21, 24, 25, 25, 25, 25, 25, 25, 25

Offset: 1

Author

Nick Loughlin, Dec 09 2008

Keywords

• easy
• nonn

Programs

Maple

# Use se(n) to find the first n terms of the sequence and te(n) to find the n-th term. se:=proc(n) local L,S,k,m,i,j: L:=[]:S:={}: for k from 1 to n do m:=ceil(sqrt(k/2)): for i from 1 to m do for j from 1 to m do if i^2+j^2<=k then S:={op(S),i^2+j^2}: fi:od:od: L:=[op(L),nops(S)]: od: end proc: te:=proc(n) local S,m,i,j: m:=ceil(sqrt(n/2)): S:={}: for i from 1 to m do for j from 1 to m do if i^2+j^2<=n then S:={op(S),i^2+j^2}: fi:od:od: return nops(S): end proc: