cp's OEIS Frontend

A056931 Difference between n-th oblong (promic) number, n(n+1), and the average of the smallest prime greater than n^2 and the largest prime less than (n+1)^2.

%I A056931 #9 Jul 02 2025 16:02:00
%S A056931 0,0,0,0,0,-1,-1,0,3,-1,-2,-1,0,1,2,1,-3,-2,0,1,1,-4,2,-2,0,3,-1,0,0,
%T A056931 -2,-3,0,-3,0,0,0,3,0,5,-4,-6,-5,-3,0,-6,1,-2,6,2,-2,1,-2,0,1,9,0,2,
%U A056931 -2,-3,2,-1,-9,1,1,2,-1,-6,-6,-1,-3,0,0,0,6,-1,-3,3,-2,-7,1,-2,1,2,-1,-4
%N A056931 Difference between n-th oblong (promic) number, n(n+1), and the average of the smallest prime greater than n^2 and the largest prime less than (n+1)^2.
%C A056931 a(1)=-0.5 which is not an integer
%F A056931 a(n) =A002378(n)-(A007491(n)+A053001(n+1))/2 =A002378(n)-A056930(n).
%e A056931 a(4)=0 because smallest prime greater than 4^2 is 17, largest prime less than 5^2 is 23, average of 17 and 23 is 20 and 4*5-20=0
%p A056931 with(numtheory): A056931 := n-> n*(n+1)-(prevprime((n+1)^2)+nextprime(n^2))/2);
%Y A056931 Cf. A002378, A007491, A053000, A053001, A056927, A056928, A056929, A056930.
%K A056931 easy,sign
%O A056931 2,9
%A A056931 _Henry Bottomley_, Jul 12 2000
%E A056931 More terms from _James Sellers_, Jul 13 2000