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A117511
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Triangular numbers for which the sum of the digits equals the sum of the digits of the next triangular number.
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1
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36, 153, 2556, 3240, 4851, 5778, 9045, 11628, 13041, 14535, 17766, 19503, 33930, 41328, 46665, 49455, 52326, 71253, 74691, 81810, 85491, 93096, 109278, 122265, 131328, 140715, 145530, 160461, 170820, 181503, 186966, 192510, 203841, 252405, 258840, 265356
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| s(n) stands for the sum of the digits of n. Each number of the sequence is divisible by 9.
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
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FORMULA
| s(a(n))=s(a(n+1))
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EXAMPLE
| 153 is in the sequence because (1) 153 is triangular number a(18), triangular number a(19)=171 and (2) 1+5+3=1+7+1
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MATHEMATICA
| Transpose[With[{c=Partition[Accumulate[Range[2000]], 2, 1]}, Select[c, Total[IntegerDigits[First[#]]]==Total[IntegerDigits[Last[#]]]&]]] [[1]] (* From Harvey P. Dale, Oct 18 2011 *)
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CROSSREFS
| Cf. A000217.
Sequence in context: A039495 A034592 A160754 * A064244 A064500 A017054
Adjacent sequences: A117508 A117509 A117510 * A117512 A117513 A117514
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KEYWORD
| base,nonn
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AUTHOR
| Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
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EXTENSIONS
| Corrected by Harvey P. Dale, Oct 18 2011
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