OFFSET
1,1
COMMENTS
See definition in comment to A175522. The definition is applied to the flattened view of the binomial coefficients with a single index, without regard to fact that A007318 is a triangle.
No more terms up to 10^6. - Michel Marcus, Feb 07 2016
EXAMPLE
MAPLE
A007318 := proc(n) option remember; local t, r; t := 0 ; for r from 0 do if t+r+1 > n then return binomial(r, n-t) ; end if; t := t+r+1 ; end do: end proc:
isA175807 := proc(n) m := 0 ; for d in numtheory[divisors](n) minus {n} do m := m+A007318(d) ; end do; m = A007318(n) ; end proc:
for n from 1 do if isA175807(n) then printf("%d, \n", n); end if; end do: # R. J. Mathar, Dec 05 2010
PROG
(PARI) b(n) = {my(m = 1); while (m*(m+1)/2 < n, m++); if (! ispolygonal(n, 3), m--); binomial(m, n - m*(m+1)/2); }
isok(n) = sumdiv(n, d, (d<n)* b(d)) == b(n); \\ Michel Marcus, Feb 07 2016
CROSSREFS
KEYWORD
nonn,less,more
AUTHOR
Vladimir Shevelev, Dec 05 2010
STATUS
approved