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A117404
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Triangular numbers for which the sum of the digits is a square.
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1
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0, 1, 10, 36, 45, 153, 171, 351, 630, 1035, 1431, 2016, 3240, 3321, 4005, 8001, 10440, 13041, 13203, 16110, 21321, 23220, 25200, 67896, 89676, 101025, 105111, 114003, 186966, 187578, 198765, 222111, 239778, 279378, 292995, 299925, 320400, 321201
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OFFSET
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1,3
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LINKS
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EXAMPLE
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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.
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MATHEMATICA
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Select[Accumulate[Range[0, 1000]], IntegerQ[Sqrt[Total[IntegerDigits[ #]]]]&] (* Harvey P. Dale, Dec 26 2014 *)
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PROG
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(PARI) isok(n) = ispolygonal(n, 3) && issquare(sumdigits(n)); \\ Michel Marcus, Feb 26 2014
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
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EXTENSIONS
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STATUS
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approved
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