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Smallest k such that remainder c(k) mod k = n, where c(k) = A002808(k) = k-th composite number or 0 if no such number exists.
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%I #8 Nov 21 2024 21:08:08

%S 4,3,0,0,0,0,8,10,11,14,19,20,25,28,29,32,37,42,43,48,51,52,57,60,65,

%T 72,75,76,79,80,83,96,99,104,105,114,115,120,125,128,133,138,139,148,

%U 149,152,153,164,175,178,179,182,187,188,197,202,207,212,213,218,221

%N Smallest k such that remainder c(k) mod k = n, where c(k) = A002808(k) = k-th composite number or 0 if no such number exists.

%F a(n)=Min{x; A065860(x)=n}

%t c[x_] := FixedPoint[x+primePi[ # ]+1&, x] t=Table[0, 100]; Do[s=Mod[c[n], n]]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

%Y Cf. A002808, A065860.

%K nonn,changed

%O 1,1

%A _Labos Elemer_, Jul 22 2002