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A073928
Smallest prime q of form q=-1+(c+1)*10^w, where c runs through composites not divisible by 3.
0
499, 89, 109, 149, 1699, 2099, 229, 25999, 269, 289999, 3299, 349, 359, 389, 409, 449, 469999999999999999, 499, 509, 52999, 5599999, 569, 58999999999999999, 6299, 64999999999999, 659, 6899, 709, 7499, 769, 77999, 809, 829, 859, 8699
OFFSET
1,1
EXAMPLE
88 is the 36th composite which is not divisible by 3; a(36)=-1+(88+1)*10^33=88999999999999999999999999999999999, i.e. 88 followed by 33 copies of digit 9.
MATHEMATICA
c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[fl=1; k=0; Do[s=(c[m]+1)*10^n-1; If[PrimeQ[s]&&(fl==1)&&!Equal[Mod[c[m], 3], 0], Print[s]; fl=0], {n, 1, 100}], {m, 1, 256}]
CROSSREFS
Sequence in context: A235528 A277785 A339622 * A045299 A106761 A243957
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Sep 03 2002
STATUS
approved