1,2

If k is a member of A027568 (both triangular and tetrahedral) then k = A000292(n-1) for some n and a(n) = 1.

Zero values are conjectures. I have searched for a(4) up to x = 10^7, a(5) up to x = 10^6 and the rest up to x = 10^4. (Wasserman)

Table of n, a(n) for n=1..104.

Cf. A087702.

Sequence in context: A052441 A221394 A025602 * A040327 A040328 A040329

Adjacent sequences: A088123 A088124 A088125 * A088127 A088128 A088129

nonn

Amarnath Murthy, Sep 26 2003

Edited and extended by David Wasserman, Jun 16 2005

approved