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A118490
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Squares for which both the sum of the digits and the product of the digits is a triangular number.
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0
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0, 1, 100, 3025, 5041, 6400, 10000, 21025, 23104, 26569, 32041, 36100, 38809, 47089, 63001, 87616, 88804, 110224, 122500, 130321, 157609, 170569, 178084, 195364, 199809, 201601, 203401, 209764, 211600, 218089, 300304, 302500, 351649, 395641
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OFFSET
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1,3
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LINKS
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Table of n, a(n) for n=1..34.
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EXAMPLE
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26569 is in the sequence because (1) it is a square, (2) the sum of its digits is 2+6+5+6+9=28, (3) the product of its digits is 2*6*8*6*9=3240, (4) 28 and 3240 are both triangular numbers.
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MATHEMATICA
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trnos=Accumulate[Range[0, 1000]];
spdQ[n_]:=Module[{idn=IntegerDigits[n]}, MemberQ[trnos, Total[idn]]&&MemberQ[trnos, Times@@idn]]; Select[Range[0, 650]^2, spdQ] (* From Harvey P. Dale, Mar 5 2011 *)
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CROSSREFS
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Cf. A000217.
Sequence in context: A075822 A200937 A112889 * A146310 A117685 A091134
Adjacent sequences: A118487 A118488 A118489 * A118491 A118492 A118493
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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), May 05 2006
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STATUS
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approved
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