

A160651


a(n) is the number of triangular nonnegative integers that are each equal to n(n+1)/2  m(m+1)/2, for some m's where 0 <= m <= n.


1



1, 2, 2, 3, 2, 2, 4, 2, 4, 2, 4, 4, 2, 4, 2, 4, 4, 2, 4, 2, 3, 6, 2, 8, 2, 2, 4, 4, 8, 2, 2, 4, 2, 4, 2, 2, 8, 4, 4, 2, 4, 8, 2, 4, 4, 4, 6, 2, 4, 6, 2, 4, 4, 6, 4, 4, 4, 4, 6, 4, 2, 8, 4, 4, 4, 2, 8, 4, 4, 2, 2, 6, 2, 4, 4, 4, 4, 4, 12, 2, 4, 4, 2, 4, 2, 2, 8, 2, 8, 4, 2, 8, 4, 8, 4, 8, 8, 2, 4, 2, 2, 8, 2, 6, 2
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,2


LINKS



FORMULA



EXAMPLE

For n = 6, the values of n(n+1)/2  m(m+1)/2, 0 <= m <= n, are 21, 20, 18, 15, 11, 6, and 0. Of these, 21, 15, 6, and 0 are triangular numbers, so a(6) = 4.


MAPLE

a:= n> add(`if`(issqr(4*(n+m+1)*(nm)+1), 1, 0), m=0..n):


PROG

(PARI) a(n) = sum(m=0, n, ispolygonal(n*(n+1)/2  m*(m+1)/2, 3)); \\ Michel Marcus, May 27 2018


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



