%I #8 Apr 14 2022 12:05:45

%S 0,1,6,15,231,276,780,861,1653,1770,2850,3003,4371,4560,5995,6216,

%T 6441,11175,14028,17205,17578,20301,20706,24090,24531,24976,28203,

%U 32640,33153,36856,37401,43071,47278,52975,54946,56953,67528,69751,76636

%N Hexagonal numbers for which the sum of the digits is also a hexagonal number.

%H Harvey P. Dale, <a href="/A117062/b117062.txt">Table of n, a(n) for n = 0..1000</a>

%e 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.

%t Module[{nn=400,hn},hn=PolygonalNumber[6,Range[0,nn]];Select[hn,MemberQ[ hn,Total[ IntegerDigits[#]]]&]] (* _Harvey P. Dale_, Apr 14 2022 *)

%o (PARI) isok(n) = ispolygonal(n, 6) && ispolygonal(sumdigits(n), 6); \\ _Michel Marcus_, Feb 26 2014

%Y Cf. A000384.

%K base,nonn

%O 0,3

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