0,3

Table of n, a(n) for n=0..38.

1770 is in the sequence because (1) it is a hexagonal number and (2)the sum of its digits 1+7+7+0=15 is also a hexagonal number.

(PARI) isok(n) = ispolygonal(n, 6) && ispolygonal(sumdigits(n), 6); \\ Michel Marcus, Feb 26 2014

Cf. A000384.

Sequence in context: A013224 A013230 A306342 * A003155 A199095 A235230

Adjacent sequences: A117059 A117060 A117061 * A117063 A117064 A117065

base,nonn

Luc Stevens (lms022(AT)yahoo.com), Apr 16 2006

approved