cp's OEIS Frontend

A161850 Subsequence of A161986 consisting of all terms that are prime.

%I A161850 #7 Sep 08 2022 08:45:45
%S A161850 7,11,13,17,19,23,29,31,37,37,41,43,47,47,53,53,59,61,67,71,71,73,79,
%T A161850 83,89,89,97,97,101,101,103,107,109,113,127,131,137,137,139,149,149,
%U A161850 151,157,163,163,167,167,173,179,179,181,193,191,193,197,199,211,223,227
%N A161850 Subsequence of A161986 consisting of all terms that are prime.
%C A161850 A161986(n) = k+r where k is n-th composite and r is remainder of (largest prime divisor of k) divided by (smallest prime divisor k).
%e A161850 A161986(1) to A161986(27) are 4, 7, 8, 9, 11, 13, 15, 17, 16, 19, 21, 22, 23, 25, 25, 27, 27, 29, 31, 32, 35, 35, 37, 37, 39, 40, 41. Hence a(1) to a(11) are the prime terms among them, namely 7, 11, 13, 17, 19, 23, 29, 31 ,37, 37, 41.
%o A161850 (Magma) [ p: n in [2..230] | not IsPrime(n) and IsPrime(p) where p is n+D[ #D] mod D[1] where D is PrimeDivisors(n) ];
%Y A161850 Cf. A161986 (A002808(n)+A161849(n)), A002808 (composite numbers), A161849 (A052369(n) mod A056608(n)), A052369 (largest prime factor of n-th composite), A056608 (smallest divisor of n-th composite).
%K A161850 nonn
%O A161850 1,1
%A A161850 _Juri-Stepan Gerasimov_, Jun 20 2009
%E A161850 Edited and corrected (a(19)=57 replaced by 67; a(38)=137, a(49)=179, a(50)=179 inserted) by _Klaus Brockhaus_, Jun 24 2009