cp's OEIS Frontend

A090302 Begin with n and consider numbers obtained by successively subtracting 0, 1, 2, 3, ...; a(n) = largest prime that arises in the process, i.e., largest prime of the form n - T(r), where T(r) is the r-th triangular number; or 0 if no such number exists.

%I A090302 #7 Dec 26 2016 15:28:18
%S A090302 0,2,3,3,5,5,7,7,3,7,11,11,13,13,5,13,17,17,19,19,11,19,23,23,19,23,
%T A090302 17,13,29,29,31,31,23,31,29,0,37,37,29,37,41,41,43,43,17,43,47,47,43,
%U A090302 47,41,37,53,53,19,53,47,43,59,59,61,61,53,61,59,11,67,67,59,67,71
%N A090302 Begin with n and consider numbers obtained by successively subtracting 0, 1, 2, 3, ...; a(n) = largest prime that arises in the process, i.e., largest prime of the form n - T(r), where T(r) is the r-th triangular number; or 0 if no such number exists.
%C A090302 a(p) = p if p is a prime.
%H A090302 T. D. Noe, <a href="/A090302/b090302.txt">Table of n, a(n) for n = 1..10000</a>
%F A090302 Largest prime of the form n - r(r+1)/2.
%Y A090302 Cf. A076768 (positions of 0's).
%Y A090302 Cf. A132399.
%K A090302 nonn
%O A090302 1,2
%A A090302 _Amarnath Murthy_, Nov 30 2003
%E A090302 More terms from _Frank Ellermann_, Dec 03 2003