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 A099151 Positive integers a such that f(3a)+f(a)=concatenation of 3a and a, where f(k)=k(k+3)/2 (A000096). 0
 5, 59, 599, 5999, 59999, 599999, 5999999, 59999999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Is it difficult to prove that the sequence continues in the expected way? LINKS EXAMPLE 599 is in the sequence because (3*599)(3*599+3)/2 + 599(602)/2 = 1797*1800/2 + 599*602/2 = 1797599. CROSSREFS Cf. A096032, A099148, A099149, A099150. Sequence in context: A106105 A178003 A036947 * A243219 A113055 A020468 Adjacent sequences:  A099148 A099149 A099150 * A099152 A099153 A099154 KEYWORD nonn,base AUTHOR John W. Layman, Sep 30 2004 EXTENSIONS Edited by Charles R Greathouse IV, Apr 29 2010 STATUS approved

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Last modified February 20 22:47 EST 2020. Contains 332086 sequences. (Running on oeis4.)