OFFSET
0,2
EXAMPLE
a(2) = 4 as all four numbers from 0 to A000217(2) = 3 can all be represented as a difference of 0,1,3, the triangular numbers from 0 to 2.
a(3) = 6 as in the seven numbers from 0 to A000217(3) = 6, six can be represented as a difference of 0,1,3,6, the triangular numbers from 0 to 3. One number, 4, cannot be.
a(6) = 17 as in the twenty-two numbers from 0 to A000217(6) = 21, seventeen can be represented as a difference of 0,1,3,6,10,15,21, the triangular numbers from 0 to 6. Five numbers, 8,13,16,17,19, cannot be.
CROSSREFS
KEYWORD
nonn
AUTHOR
Scott R. Shannon, Jun 09 2020
STATUS
approved