1,3

Table of n, a(n) for n=1..72.

Select[Range[0, 88], FreeQ[Differences[IntegerDigits[(#^2+#)/2]], 0]&] (* Jayanta Basu, May 31 2013 *)

Cf. A043096, A000217, A050760.

Sequence in context: A118766 A136399 A056167 * A039274 A102487 A343951

Adjacent sequences: A050756 A050757 A050758 * A050760 A050761 A050762

nonn,base

Patrick De Geest, Sep 15 1999

Name clarified and offset changed to 1 by Jon E. Schoenfield, Oct 16 2019

approved