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 A229262 Smallest triangular number whose decimal expansion ends (nontrivially) with the n-th triangular number. 1
 21, 153, 36, 210, 2415, 3321, 528, 136, 2145, 3655, 666, 378, 1891, 6105, 205120, 185136, 10153, 399171, 63190, 78210, 364231, 5253, 210276, 180300, 11325, 406351, 1378, 81406, 357435, 4465, 215496, 18528, 12561, 413595, 57630, 84666, 65703, 3741, 220780 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Shyam Sunder Gupta, Table of n, a(n) for n = 1..200 EXAMPLE a(4)=210 because 210 is the smallest triangular number that ends with 4th triangular number i.e. 10. MATHEMATICA TriangularQ[n_Integer?Positive] := IntegerQ[Sqrt[8*n + 1]]; f[n_] := (k = 1; While[a = ToExpression[ ToString[k] <> ToString[n]]; ! TriangularQ[a], k++ ]; a); Table[f[ n*(n + 1)/2], {n, 1, 50}] CROSSREFS Cf. A000217. Sequence in context: A239569 A219599 A221694 * A184376 A184368 A078396 Adjacent sequences: A229259 A229260 A229261 * A229263 A229264 A229265 KEYWORD nonn,base AUTHOR Shyam Sunder Gupta, Sep 17 2013 STATUS approved

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Last modified February 1 06:22 EST 2023. Contains 359981 sequences. (Running on oeis4.)