OFFSET
1,2
EXAMPLE
a(5) = 8 subsets: {1}, {3}, {6}, {10}, {15}, {6, 15}, {1, 3, 6} and {3, 10, 15}.
PROG
(Python)
from math import isqrt
from functools import cache
def cond(s): k = 8*s+1; return s > 0 and isqrt(k)**2 == k
def u(n): return n*(n+1)//2
@cache
def b(n, s):
if n == 0: return int(cond(s))
return b(n-1, s) + b(n-1, s+u(n))
a = lambda n: b(n, 0)
print([a(n) for n in range(1, 51)]) # Michael S. Branicky, Oct 18 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 17 2024
EXTENSIONS
a(23) and beyond from Michael S. Branicky, Oct 18 2024
STATUS
approved
