A073928 Smallest prime q of form q=-1+(c+1)*10^w, where c runs through composites not divisible by 3.

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

Links

Table of n, a(n) for n=1..35.

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

Cf. A055785, A002808.

Sequence in context: A235528 A277785 A339622 * A045299 A106761 A243957

Adjacent sequences: A073925 A073926 A073927 * A073929 A073930 A073931

Keyword

base,nonn

Author

Labos Elemer, Sep 03 2002

Status

approved