OFFSET
1,2
COMMENTS
Similar to A248983 except a(1) = 0, the zeroth triangular number.
FORMULA
Empirical g.f.: x^2*(66*x^16-66*x^15-153*x^14+153*x^13+91*x^12-91*x^11-3*x^2-x-2) / ((x-1)^3*(x+1)^3). - Colin Barker, Oct 24 2014
PROG
(PARI) v=[]; n=0; while(n<5000, num=(vecsum(v)+n); if(num%(#v+1)==0&&vecsearch(vecsort(v), n)==0, for(i=0, n, if(i*(i+1)/2>(num/(#v+1)), break); if(i*(i+1)/2==(num/(#v+1)), print1(n, ", "); v=concat(v, n); n=0; break))); n++)
CROSSREFS
KEYWORD
nonn
AUTHOR
Derek Orr, Oct 23 2014
STATUS
approved