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A066567
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Numbers that when incremented by the product of their digits produce a square.
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4
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2, 8, 13, 63, 91, 100, 128, 185, 215, 221, 337, 400, 448, 456, 549, 551, 559, 681, 900, 1024, 1089, 1151, 1185, 1215, 1221, 1327, 1348, 1437, 1600, 1651, 1897, 2025, 2112, 2191, 2196, 2209, 2293, 2304, 2392, 2401, 2448, 2500, 2539, 2544, 2551, 2596, 2601
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OFFSET
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1,1
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LINKS
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EXAMPLE
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63 belongs to this sequence as 63 + 6*3 = 81 = 9^2.
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MATHEMATICA
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f[n_] := n + Apply[ Times, IntegerDigits[n]]; Select[ Range[ 2500], IntegerQ[ Sqrt[ f[ # ]]] & ]
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PROG
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(PARI) ProdD(x)= { local(p=1); while (x>9 && p>0, p*=x%10; x\=10); return(p*x) } { n=0; for (m=1, 10^10, if (issquare(m + ProdD(m)), write("b066567.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Mar 05 2010
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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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EXTENSIONS
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STATUS
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approved
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