The OEIS is supported by the many generous donors to the OEIS Foundation.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #9 Dec 26 2014 12:49:33
%S 0,1,10,36,45,153,171,351,630,1035,1431,2016,3240,3321,4005,8001,
%T 10440,13041,13203,16110,21321,23220,25200,67896,89676,101025,105111,
%U 114003,186966,187578,198765,222111,239778,279378,292995,299925,320400,321201
%N Triangular numbers for which the sum of the digits is a square.
%H Harvey P. Dale, <a href="/A117404/b117404.txt">Table of n, a(n) for n = 1..10000</a>
%e 45 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 4+5=9 is a square.
%t Select[Accumulate[Range[0,1000]],IntegerQ[Sqrt[Total[IntegerDigits[ #]]]]&] (* _Harvey P. Dale_, Dec 26 2014 *)
%o (PARI) isok(n) = ispolygonal(n, 3) && issquare(sumdigits(n)); \\ _Michel Marcus_, Feb 26 2014
%Y Cf. A000217.
%K base,nonn
%O 1,3
%A Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
%E Corrected by _Michel Marcus_, Feb 26 2014