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 A271584 Irregular triangle read by rows: alternate (k-1)*k, k^2, for k = 0 to n. 1
 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 1, 4, 0, 0, 2, 6, 0, 1, 4, 9, 0, 0, 2, 6, 12, 0, 1, 4, 9, 16, 0, 0, 2, 6, 12, 20, 0, 1, 4, 9, 16, 25, 0, 0, 2, 6, 12, 20, 30, 0, 1, 4, 9, 16, 25, 36, 0, 0, 2, 6, 12, 20, 30, 42, 0, 1, 4, 9, 16, 25, 36, 49 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,9 COMMENTS This is the irregular triangle e(n) mentioned in A269837. Last number: 0, 0, 0, 1, 2, 4, 6, 9, 12, 16, 20, 25, ... = A002620 with a third initial 0. Row sums: 0, 0, 0, 1, 2, 5, 8, 14, 20, 30, 40, ... = A006918 with three initial 0. Columns: the sum of the first two terms is A000384(n). LINKS Table of n, a(n) for n=0..71. EXAMPLE Irregular triangle: 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 1, 4, 0, 0, 2, 6, 0, 1, 4, 9, 0, 0, 2, 6, 12, 0, 1, 4, 9, 16, 0, 0, 2, 6, 12, 20, 0, 1, 4, 9, 16, 25, etc. MATHEMATICA Flatten[Transpose /@ Table[{k (k - 1), k^2}, {n, 0, 7}, {k, 0, n}]] (* Michael De Vlieger, Apr 10 2016 *) CROSSREFS Cf. A000290, A000384, A002262, A006918, A161680, A269837. Sequence in context: A257920 A258210 A258228 * A072737 A061290 A099096 Adjacent sequences: A271581 A271582 A271583 * A271585 A271586 A271587 KEYWORD nonn,tabf AUTHOR Paul Curtz, Apr 10 2016 STATUS approved

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Last modified June 15 19:43 EDT 2024. Contains 373410 sequences. (Running on oeis4.)