cp's OEIS Frontend

A106613 Nonprimes of the form r(r(r(n)+1)+1)+1, where A141468(n)=r(n)=n-th nonprime.

%I A106613 #4 Mar 30 2012 18:52:25
%S A106613 1,15,25,26,34,36,40,45,49,51,52,55,56,57,63,65,69,70,76,77,78,81,86,
%T A106613 87,88,91,93,94,95,105,106,112,116,117,118,119,121,123,124,125,133,
%U A106613 135,143,145,146,153,154,155,159,160,161,162,165,169,170,172,175,177,183,185
%N A106613 Nonprimes of the form r(r(r(n)+1)+1)+1, where A141468(n)=r(n)=n-th nonprime.
%e A106613 If n=1, then
%e A106613 r(r(r(1)+1)+1)+1=r(r(0+1)+1)+1=r(r(1)+1)+1=r(0+1)+1=r(1)+1=0+1=1=a(1).
%e A106613 If n=2, then
%e A106613 r(r(r(2)+1)+1)+1=r(r(1+1)+1)+1=r(r(2)+1)+1=r(1+1)+1=r(2)+1=1+1=2
%e A106613 (prime).
%e A106613 If n=3, then
%e A106613 r(r(r(3)+1)+1)+1=r(r(4+1)+1)+1=r(r(5)+1)+1=r(8+1)+1=r(9)+1=14+1=15=a(2).
%e A106613 If n=4, then
%e A106613 r(r(r(4)+1)+1)+1=r(r(6+1)+1)+1=r(r(7)+1)+1=r(10+1)+1=r(11)+1=16+1=17
%e A106613 (prime).
%e A106613 If n=5, then
%e A106613 r(r(r(5)+1)+1)+1=r(r(8+1)+1)+1=r(r(9)+1)+1=r(14+1)+1=r(15)+1=22+1=23
%e A106613 (prime).
%e A106613 If n=6, then
%e A106613 r(r(r(6)+1)+1)+1=r(r(9+1)+1)+1=r(r(10)+1)+1=r(15+1)+1=r(16)+1=24+1=25=a(3).
%e A106613 If n=7, then
%e A106613 r(r(r(7)+1)+1)+1=r(r(10+1)+1)+1=r(r(11)+1)+1=r(16+1)+1=r(17)+1=25+1=26=a(4).
%e A106613 If n=8, then
%e A106613 r(r(r(8)+1)+1)+1=r(r(12+1)+1)+1=r(r(13)+1)+1=r(20+1)+1=r(21)+1=30+1=31
%e A106613 (prime).
%e A106613 If n=9, then
%e A106613 r(r(r(9)+1)+1)+1=r(r(14+1)+1)+1=r(r(15)+1)+1=r(22+1)+1=r(23)+1=33+1=34=a(5).
%e A106613 If n=10, then
%e A106613 r(r(r(10)+1)+1)+1=r(r(15+1)+1)+1=r(r(16)+1)+1=r(24+1)+1=r(25)+1=35+1=36=a(6),
%e A106613 etc.
%Y A106613 Cf. A000040, A141468.
%K A106613 nonn
%O A106613 1,2
%A A106613 _Juri-Stepan Gerasimov_, Aug 25 2008
%E A106613 28 removed, 93 added, 126 removed by _R. J. Mathar_, Sep 05 2008