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 A245798 Catalan number analogs for totienomial coefficients (A238453). 3
 1, 1, 2, 4, 12, 36, 120, 360, 960, 3840, 13824, 41472, 152064, 506880, 2280960, 7983360, 29937600, 99792000, 266112000, 1197504000, 4790016000, 19160064000, 73156608000, 219469824000, 1009561190400, 3533464166400, 12563428147200, 54441521971200, 155547205632000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS One definition of the Catalan numbers is binomial(2*n,n) / (n+1); the current sequence models this definition using the generalized binomial coefficients arising from Euler's totient function (A000010). When the INTEGERS (2014) paper was written it was not known that this was an integral sequence (see the final paragraph of that paper). However, it is now known to be integral. Another name could be phi-Catalan numbers. - Tom Edgar, Mar 29 2015 LINKS Tom Edgar, Table of n, a(n) for n = 0..28 Tom Edgar, Totienomial Coefficients, INTEGERS, 14 (2014), #A62. Tom Edgar and Michael Z. Spivey, Multiplicative functions, generalized binomial coefficients, and generalized Catalan numbers, Journal of Integer Sequences, Vol. 19 (2016), Article 16.1.6. FORMULA a(n) = A238453(2*n,n) / A000010(n+1). EXAMPLE We see that A238453(10,5) = 72 and A000010(5+1) = 2, so a(5) = (1/2)*72 = 36. PROG (Sage) [(1/euler_phi(n+1))*prod(euler_phi(i) for i in [1..2*n])/prod(euler_phi(i) for i in [1..n])^2 for n in [0..100]] CROSSREFS Cf. A000010, A238453, A000108, A001088. Sequence in context: A117757 A009623 A148208 * A241530 A123071 A048116 Adjacent sequences:  A245795 A245796 A245797 * A245799 A245800 A245801 KEYWORD nonn AUTHOR Tom Edgar, Aug 22 2014 STATUS approved

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Last modified May 9 13:42 EDT 2021. Contains 343742 sequences. (Running on oeis4.)