1,3

The first two are zero because the Ulam sequence (A002858) is initialized for those terms. The terms of the sum are in A080328 and A080329 and the indices are in A080330 and A080331.

Table of n, a(n) for n=1..71.

The 11th Ulam number (26) is the sum of the 6th Ulam number (8) and the 10th Ulam number (18), so a(11)=10.

Cf. A002858, A080328, A080329, A080330.

Sequence in context: A291579 A331300 A274933 * A297247 A167463 A053835

Adjacent sequences: A080328 A080329 A080330 * A080332 A080333 A080334

nonn

Jud McCranie, Feb 15 2003

approved