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 A340595 a(n) is the least k for which A340594(k) = n. 2
 2, 4, 8, 21, 42, 65, 80, 217, 488, 721, 2120, 2349, 2796, 9214, 16043, 23287, 28626, 43588, 58176, 116982, 213435, 444329, 640673, 967248, 1399895, 1449156, 1528785, 2768054, 2915135, 3631071, 3673118, 5032731, 12977420 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS a(n) is the least k >= 2 from which it takes exactly n iterations of A340592 to reach 0, 1 or a prime. LINKS Table of n, a(n) for n=0..32. EXAMPLE Starting from 21, it takes 3 iterations of A340592 to reach 0,1 or a prime: 21 -> 16 -> 14 -> 13. Since this is the first case where 3 iterations are required, a(3) = 21. MAPLE dcat:= proc(L) local i, x; x:= L[-1]; for i from nops(L)-1 to 1 by -1 do x:= 10^(1+ilog10(x))*L[i]+x od; x end proc: f:= proc(n) local F; F:= sort(ifactors(n)[2], (a, b) -> a[1] < b[1]); dcat(map(t -> t[1]\$t[2], F)) mod n; end proc: g:= proc(n) option remember; if isprime(n) then 0 else 1 + procname(f(n)) fi end proc: g(0):= 0: g(1):= 0: V:= Array(0..30): count:= 0: for n from 2 while count < 31 do v:= f(n); if v::integer and v <= 100 and V[v] = 0 then count:= count+1; V[v]:= n; fi od: convert(V, list); CROSSREFS Cf. A340592, A340594. Sequence in context: A309868 A059731 A001315 * A216643 A002040 A162110 Adjacent sequences: A340592 A340593 A340594 * A340596 A340597 A340598 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Jan 13 2021 STATUS approved

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Last modified February 25 02:17 EST 2024. Contains 370308 sequences. (Running on oeis4.)