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 A153833 Atavistic Index Sequence to A089840 computed for SPINE. 9
 0, 21, 3613, 3771, 3906, 3929, 3783 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Recursive transformation SPINE for Catalan bijections has a well-defined inverse (see the definition & comments at A122203). For all Catalan bijections in A089840 that inverse produces a bijection which is itself in A089840. This sequence gives the indices to those positions where each ("primitive", non-recursive bijection) of A089840(n) occurs "atavistically" amongst the more complex recursive bijections in A122203. I.e. A122203(a(n)) = A089840(n). Similarly, other "atavistic forms" resurface as: A122288(a(n)) = A122202(n), A122285(a(n)) = A122204(n) and A122201(a(n)) = A122283(n). See also comments at A153832. Other known terms: a(17)-a(44): 65352, 65359, 65604, 65739, 251, 1656303, 1656426, 1656552, 1656628, 1656479, 1661655, 1661816, 1666720, 1684006, 1684221, 1667042, 1667007, 1684152, 1661799, 1661676, 1666759, 1684081, 1684437, 1667151, 1684509, 1667187, 1661961, 1661944. LINKS FORMULA a(n) = A089839bi(A153834(A089843(n)),n) CROSSREFS Cf. A153832, A089839. Sequence in context: A340331 A202980 A221722 * A221164 A264250 A250064 Adjacent sequences:  A153830 A153831 A153832 * A153834 A153835 A153836 KEYWORD nonn AUTHOR Antti Karttunen, Jan 07 2009 STATUS approved

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Last modified June 15 13:25 EDT 2021. Contains 345048 sequences. (Running on oeis4.)