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 A117511 Triangular numbers for which the sum of the digits equals the sum of the digits of the next triangular number. 1
 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; text; internal format)
 OFFSET 1,1 COMMENTS s(n) stands for the sum of the digits of n. Each number of the sequence is divisible by 9. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 FORMULA s(a(n))=s(a(n+1)) 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 MATHEMATICA Transpose[With[{c=Partition[Accumulate[Range[2000]], 2, 1]}, Select[c, Total[IntegerDigits[First[#]]]==Total[IntegerDigits[Last[#]]]&]]] [[1]] (* Harvey P. Dale, Oct 18 2011 *) (#(#+1))/2&/@(SequencePosition[Total[IntegerDigits[#]]&/@Accumulate[ Range[ 1000]], {x_, x_}][[All, 1]]) (* Harvey P. Dale, Mar 02 2022 *) CROSSREFS Cf. A000217. Sequence in context: A034592 A160754 A275496 * A250632 A211728 A211737 Adjacent sequences:  A117508 A117509 A117510 * A117512 A117513 A117514 KEYWORD base,nonn AUTHOR Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006 EXTENSIONS Corrected by Harvey P. Dale, Oct 18 2011 STATUS approved

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Last modified May 16 15:08 EDT 2022. Contains 353706 sequences. (Running on oeis4.)