

A192530


Indexlist (modified) of the primes generated at A192583.


3



1, 2, 3, 3, 4, 5, 6, 7, 9, 11, 12, 13, 15, 16, 19, 22, 23, 24, 27, 28, 33, 34, 35, 39, 41, 48, 57, 61, 66, 72, 95, 102, 114, 117, 128, 143, 148, 184, 196, 227, 228, 266, 302, 325, 367, 417, 471, 606, 882, 916, 1071, 1539, 4305
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OFFSET

1,2


COMMENTS

Besides the generated primes 2,5,11,13,17,..., the initial numbers 4,6,8 in A192583 are represented here by index of nearest lower prime.


LINKS

Table of n, a(n) for n=1..53.


EXAMPLE

A192583=(2,4,5,6,8,11,13,17,23,...). a(1)=1 because the index of 2 is 1; a(2)=2 because, for term #2 of A192530, which is 4, the nearest prime <4 is 3, which has index 2; a(3)=3 because the index of 5 is 3. ("Nearest prime down" for nonprimes is given by PrimePi in the Mathematica program.)


MATHEMATICA

start = {2, 4, 6, 8}; primes = Table[Prime[n], {n, 1, 10000}];
f[x_, y_] := If[MemberQ[primes, x*y + 1], x*y + 1]
b[x_] :=
Block[{w = x},
Select[Union[
Flatten[AppendTo[w,
Table[f[w[[i]], w[[j]]], {i, 1, Length[w]}, {j, 1, i}]]]], # <
10000000 &]];
t = FixedPoint[b, start] (* A192583 *)
PrimePi[t] (* A192530 Nonprimes 4, 6, 8 are represented by "next prime down". *)


CROSSREFS

Cf. A192583.
Sequence in context: A039732 A011876 A029036 * A281744 A026838 A182229
Adjacent sequences: A192527 A192528 A192529 * A192531 A192532 A192533


KEYWORD

nonn,fini,full


AUTHOR

Clark Kimberling, Jul 04 2011


STATUS

approved



