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 A215655 Irregular triangle read by rows: reading the n-th row describes all the numbers seen in the triangle up to the end of the n-th row. 0
 2, 2, 4, 2, 2, 4, 6, 2, 4, 4, 2, 6, 8, 2, 6, 4, 4, 6, 2, 8, 10, 2, 8, 4, 6, 6, 4, 8, 2, 10, 12, 2, 10, 4, 8, 6, 6, 8, 4, 10, 2, 12, 14, 2, 12, 4, 10, 6, 8, 8, 6, 10, 4, 12, 2, 14, 16, 2, 14, 4, 12, 6, 10, 8, 8, 10, 6, 12, 4, 14, 2, 16, 18, 2, 16, 4, 14, 6, 12, 8, 10, 10, 8, 12, 6, 14, 4, 16, 2, 18, 20, 2, 18, 4, 16, 6, 14, 8, 12, 10, 10, 12, 8, 14, 6, 16, 4, 18, 2, 20 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Given the initial row "2 2", is the rest of the triangle forced? If not, should this version have an additional clause in the definition saying "lexicographically earliest, given the first row"? Eric Angelini asks if there is a similar triangle (self-describing and infinite) that contains at least one odd number. REFERENCES Eric Angelini, Posting to the Sequence Fans Mailing List, Oct 29 2012. LINKS EXAMPLE Triangle begins: 2 2 4 2  2 4 6 2  4 4  2 6 8 2  6 4  4 6  2 8 10 2  8 4  6 6  4 8  2 10 12 2 10 4  8 6  6 8  4 10  2 12 14 2 12 4 10 6  8 8  6 10  4 12  2 14 16 2 14 4 12 6 10 8  8 10  6 12  4 14  2 16 18 2 16 4 14 6 12 8 10 10  8 12  6 14  4 16  2 18 20 2 18 4 16 6 14 8 12 10 10 12  8 14  6 16  4 18  2 20 ... Top line says: I see  two integers "2" so far Next line says: I see four integers "2" and two integers "4" so far Next line says: I see  six integers "2", four integers "4" and two integers "6" so far etc. The counts are thus cumulative. And the (easy-to-build) array infinite. CROSSREFS Cf. A005150. Sequence in context: A276604 A072301 A127171 * A118232 A115070 A064145 Adjacent sequences:  A215652 A215653 A215654 * A215656 A215657 A215658 KEYWORD nonn,tabf AUTHOR N. J. A. Sloane, Feb 17 2013 STATUS approved

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Last modified May 26 13:13 EDT 2020. Contains 334626 sequences. (Running on oeis4.)