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 A308476 a(1) = 1; a(n) = Sum_{k=1..n-1, gcd(n,k) = 1} Stirling2(n,k)*a(k). 1
 1, 1, 4, 25, 366, 5491, 176569, 5332097, 276268942, 13470365431, 1135683784753, 75066413338423, 9256260956838520, 918768523598548169, 140268128758724744770, 18398287904991375995745, 3879391299475140314514162, 594721341754741064012714341 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS G. C. Greubel, Table of n, a(n) for n = 1..250 MAPLE a := proc(n) local j; option remember; if n = 1 then 1; else add(`if`(gcd(n, j) = 1, Stirling2(n, j)*a(j), 0), j = 1 .. n - 1); end if; end proc; seq(a(n), n = 1 .. 30); # G. C. Greubel, Mar 08 2021 MATHEMATICA a[n_] := Sum[If[GCD[n, k] == 1, StirlingS2[n, k] a[k], 0], {k, 1, n - 1}]; a[1] = 1; Table[a[n], {n, 1, 18}] PROG (Sage) @CachedFunction def a(n): if n==1: return 1 else: return sum( stirling_number2(n, j)*a(j) if gcd(n, j)==1 else 0 for j in (1..n-1) ) [a(n) for n in (1..30)] # G. C. Greubel, Mar 08 2021 CROSSREFS Cf. A005121, A045545, A308463. Sequence in context: A222982 A259591 A093959 * A222902 A086216 A167041 Adjacent sequences: A308473 A308474 A308475 * A308477 A308478 A308479 KEYWORD nonn AUTHOR Ilya Gutkovskiy, May 29 2019 STATUS approved

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Last modified December 6 18:39 EST 2022. Contains 358644 sequences. (Running on oeis4.)