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A028839
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Sum of digits of n is a square.
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21
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1, 4, 9, 10, 13, 18, 22, 27, 31, 36, 40, 45, 54, 63, 72, 79, 81, 88, 90, 97, 100, 103, 108, 112, 117, 121, 126, 130, 135, 144, 153, 162, 169, 171, 178, 180, 187, 196, 202, 207, 211, 216, 220, 225, 234, 243, 252, 259, 261, 268, 270, 277, 286, 295, 301, 306, 310
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OFFSET
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1,2
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COMMENTS
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Difference between two consecutive terms is never equal to 8. - Carmine Suriano, Mar 31 2014
In this sequence, there is no number of the form 3*k-1. In other words, if a(n) is not divisible by 9, it must be of the form 3*k+1. - Altug Alkan, Apr 08 2016
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LINKS
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EXAMPLE
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234511 belongs to the sequence as its sum of digits is 16, a square.
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MATHEMATICA
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Select[ Range[ 500 ], IntegerQ[ Sqrt[ Apply[ Plus, IntegerDigits[ # ] ] ] ]& ]
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PROG
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(Magma) [n: n in [1..400] | IsSquare(&+Intseq(n))]; // Bruno Berselli, May 26 2011
(PARI) isok(n) = issquare(sumdigits(n)); \\ Michel Marcus, Oct 30 2014
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CROSSREFS
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Cf. A053057 (squares whose digit sum is also a square).
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KEYWORD
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nonn,base,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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