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 A209686 For each n, define a sequence of numbers by S(0)=n, S(i) = sum of last three digits of the concatenation S(0)S(1)S(2)...S(i-1); a(n) = smallest m such that S(m) = 11, or -1 if 11 is never reached. 1
 -1, 6, 8, 14, 7, 6, 13, 16, 6, 7, 5, 0, 3, 8, 6, 13, 16, 6, 7, 7, 15, 11, 7, 6, 13, 16, 6, 7, 9, 1, 9, 15, 6, 13, 16, 6, 7, 12, 1, 10, 4, 6, 13, 16, 6, 7, 9, 1, 2, 4, 6, 13, 16, 6, 7, 5, 1, 20, 13, -1, 13, 16, 6, 7, 4, 1, 12, 2, 5, 3, 16, 6, 7, 10, 1, 3, 11, 15, 6, 13, 6, 7, 19, 1, 14, 6, 2, 7, 5, 9, 7, 9, 1, 12, 4, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES Eric Angelini, Posting to Math Fun Mailing List, Mar 11 2012. LINKS EXAMPLE 3->3->6->12->9->12->12->5->8->15->14->10->5->6->11, so a(3)=14. 59->14->14->9->14->14->9->... never reaches 11, so a(59)=-1. CROSSREFS Cf. A209674. Sequence in context: A315877 A315878 A101729 * A283286 A283375 A242758 Adjacent sequences:  A209683 A209684 A209685 * A209687 A209688 A209689 KEYWORD sign,base AUTHOR N. J. A. Sloane, Mar 11 2012 STATUS approved

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Last modified June 25 10:29 EDT 2019. Contains 324351 sequences. (Running on oeis4.)