cp's OEIS Frontend

A275415 Pairs of primes (p, q) such that |2p - 3q| = 1.

%I A275415 #25 Aug 25 2016 03:10:26
%S A275415 5,3,7,5,11,7,17,11,19,13,29,19,43,29,47,31,61,41,71,47,79,53,89,59,
%T A275415 101,67,107,71,109,73,151,101,163,109,191,127,197,131,223,149,227,151,
%U A275415 251,167,269,179,271,181,317,211,349,233,359,239,421,281,439,293
%N A275415 Pairs of primes (p, q) such that |2p - 3q| = 1.
%C A275415 We observe that a(2n-1) = A265761(n+1) and a(2n) = A222565(n+1).
%e A275415 The first pair (5, 3) is in the sequence because |2*5 - 3*3| = 1;
%e A275415 The second pair (7, 5) is in the sequence because |2*7 - 3*5|= 1.
%p A275415 nn:=100:for i from 3 to nn do:
%p A275415 p:=ithprime(i):r:=irem(p,3):q:=(2*p + (-1)^(r+1))/3:
%p A275415   if isprime(q)
%p A275415    then
%p A275415   printf(`%d, `,p): printf(`%d, `,q):
%p A275415   else
%p A275415   fi:
%p A275415 od:
%o A275415 (PARI) lista(n)=forprime(i=3,n,j=(1.5*i)\1;j+=((j+1)%2);if(isprime(j),print1(j", "i", "))) \\ _David A. Corneth_, Aug 09 2016
%Y A275415 Cf. A222565, A265761.
%K A275415 nonn
%O A275415 1,1
%A A275415 _Michel Lagneau_, Aug 09 2016