cp's OEIS Frontend

A276269 a(n) = n + the largest (if n is even), or the smallest (if n is odd) prime factor of n if n > 1; and a(1)=1.

%I A276269 #6 Aug 26 2016 12:33:03
%S A276269 1,4,6,6,10,9,14,10,12,15,22,15,26,21,18,18,34,21,38,25,24,33,46,27,
%T A276269 30,39,30,35,58,35,62,34,36,51,40,39,74,57,42,45,82,49,86,55,48,69,94,
%U A276269 51,56,55,54,65,106,57,60,63,60,87,118,65,122,93,66,66,70,77,134
%N A276269 a(n) = n + the largest (if n is even), or the smallest (if n is odd) prime factor of n if n > 1; and a(1)=1.
%C A276269 This is the underlying sequence for sequence A256393.
%C A276269 a(n) is never prime, since for n>1 it is alternatively divisible by A006530(n) then by A020639(n). This explains the existence of the sequences noted [p] in A256393 comments. There are also such [c] sequences where c is composite like for instance for c=8.
%o A276269 (PARI) a(n) = if (n==1, 1, my(f = factor(n)); if (n % 2, n + f[1,1], n + f[#f~, 1]));
%Y A276269 Cf. A006530 (Gpf), A020639 (Lpf), A256393.
%K A276269 nonn
%O A276269 1,2
%A A276269 _Michel Marcus_, Aug 26 2016