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

1,5

Links

Table of n, a(n) for n=1..80.

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:

Crossrefs

Sequence in context: A227145 A039730 A257807 * A176844 A085182 A211339

Adjacent sequences: A152592 A152593 A152594 * A152596 A152597 A152598

Keyword

easy,nonn

Author

Nick Loughlin, Dec 09 2008

Status

approved