A073258 Numbers n such that gcd(c(n),n) = gcd(A002808(n),n) = A064814(n)=1 where c(n) is the n-th composite number.
1, 3, 4, 8, 9, 11, 13, 17, 19, 23, 25, 27, 29, 31, 33, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 53, 57, 58, 59, 61, 66, 67, 68, 69, 71, 73, 79, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 94, 95, 97, 100, 101, 103, 106, 107, 108, 109, 111, 113, 115, 116, 117, 118, 119
Offset: 1
Keywords
Examples
n=256: composite(256) = 323 = 17*19, gcd(323,256)=1, so 256 is a term.
Programs
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Mathematica
c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x]; t=Table[0, {256}]; s=0; k=0; Do[s=GCD[c[n], n]; If[Equal[s, 1], k=k+1; t[[k]]=n; Print[{k, n}]], {n, 1, 256}] t -
PARI
lista(nn) = {my(n=0, list=List()); forcomposite (c=1, nn, n++; if (gcd(n, c) == 1, listput(list, c))); Vec(list); } \\ Michel Marcus, Jul 19 2020