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 A056557 Second tetrahedral co-ordinate. 13
 0, 0, 1, 1, 0, 1, 1, 2, 2, 2, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,8 COMMENTS If {(X,Y,Z)} are triples of nonnegative integers with X>=Y>=Z ordered by X, Y and Z, then X=A056556(n), Y=A056557(n) and Z=A056558(n) LINKS FORMULA a(n) =floor[(sqrt(8*(n-A056556(n)*(A056556(n)+1)*(A056556(n)+2)/6)+1)-1)/2] =A003056(n-A000292(A056556(n)-1)) a(n+1) = A056556(n)==A056558(n) ? 0 : a(n)==A056558(n) ? a(n)+1 : a(n). - Graeme McRae, Jan 09 2007 CROSSREFS Cf. A000292, A002262, A003056, A056556, A056558, A056559, A056560. See also A194847, A194848. Sequence in context: A071471 A020943 A300075 * A302986 A295305 A082900 Adjacent sequences:  A056554 A056555 A056556 * A056558 A056559 A056560 KEYWORD nonn AUTHOR Henry Bottomley, Jun 26 2000 STATUS approved

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Last modified October 18 14:52 EDT 2019. Contains 328161 sequences. (Running on oeis4.)