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 A308475 a(1) = 1; a(n) = Sum_{k=1..n-1, gcd(n,k) = 1} binomial(n,k)*a(k). 0
 1, 2, 9, 40, 315, 1896, 21651, 191360, 2546487, 28064080, 488517183, 5879603280, 124673371719, 1928346159572, 42684093159480, 754925802649360, 20289814995554811, 366300418631427144, 11352374441063693655, 250187625076714423520, 7774760839170720287739 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS MATHEMATICA a[n_] := Sum[If[GCD[n, k] == 1, Binomial[n, k] a[k], 0], {k, 1, n - 1}]; a[1] = 1; Table[a[n], {n, 1, 21}] CROSSREFS Cf. A000670, A045545, A052882, A056188. Sequence in context: A220471 A213095 A238372 * A002825 A259339 A052322 Adjacent sequences:  A308472 A308473 A308474 * A308476 A308477 A308478 KEYWORD nonn AUTHOR Ilya Gutkovskiy, May 29 2019 STATUS approved

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Last modified October 23 07:11 EDT 2019. Contains 328336 sequences. (Running on oeis4.)