%I
%S 1,4,6,18,2,7,1,4,1,2,4,5,5,3,1,2,2,5,3,3,4,3,1,10,1,1,8,3,4,7,5,12,
%T 10,8,9,7,3,5,3,6,3,10,11,1,2,13,9,6,3,2,1,2,3,3,2,2,6,13,9,4,1,11,1,
%U 3,8,9,1,4,6,3,8,3,5,2,3,2,5,1,14,9
%N Successive differences of index of triangular numbers sum of two pentagonal numbers.
%C The behavior of this sequence is unexpectedly quite complex.
%H Peter Kagey, <a href="/A332986/b332986.txt">Table of n, a(n) for n = 1..2500</a>
%Y Cf. A000217 (triangular numbers), A000326 (pentagonal numbers), A332987 (sums of two nonzero pentagonal numbers), A333009 (analog for indices of square numbers).
%Y Cf. First differences of A332985.
%K nonn
%O 1,2
%A _Olivier GĂ©rard_, Mar 05 2020
