cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A327592 Smallest prime (p) of six consecutive primes (p,q,r,u,v,w) for which the conic section discriminant (Delta) is a perfect square.

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%I A327592 #29 Oct 18 2019 01:03:57
%S A327592 397,68219,87881,316531,430487,440653,639701,691813,732497,982981,
%T A327592 1145773,1226683,1288337,1291223,1537751,1563943,1756663,1913803,
%U A327592 2043397,2134589,2143391,2317097,2366789,2528833,3047311,3107597,3261523,3678869,3884389,4143397
%N A327592 Smallest prime (p) of six consecutive primes (p,q,r,u,v,w) for which the conic section discriminant (Delta) is a perfect square.
%C A327592 Delta = pqr + 2uvw - pu^2 - qv^2 - rw^2 for the general conic section px^2 + qy^2 + rz^2 + 2uyz + 2vxz + 2wxy = 0.
%C A327592 Perfect squares of this form are quite rare, representing approximately 0.0048% of possible Delta values using consecutive prime number coefficients. (First 4 million primes tested.)
%H A327592 Giovanni Resta, <a href="/A327592/b327592.txt">Table of n, a(n) for n = 1..10000</a> (first 192 terms from Philip Mizzi)
%e A327592 48 = sqrt(2304) = pqr + 2uvw - pu^2 - qv^2 - rw^2 for (p,q,r,u,v,w) = (440653,440669,440677,440681,440683,440711), which are consecutive primes. Hence, 440653 is a member of the sequence.
%t A327592 f[{p_, q_, r_, u_, v_, w_}] := p q r + 2 u v w - p u^2 - q v^2 - r w^2; First /@ Select[Partition[ Prime@ Range@ 300000, 6, 1], IntegerQ@ Sqrt@ f@ # &] (* _Giovanni Resta_, Sep 30 2019 *)
%o A327592 (PARI) chk(nn) = {forprime (p=1, nn, my(q = nextprime(p+1), r = nextprime(q+1), u = nextprime(r+1), v = nextprime(u+1), w = nextprime(v+1)); if (issquare(p*q*r + 2*u*v*w - p*u^2 - q*v^2 - r*w^2), print1(p, ", ")););} \\ _Michel Marcus_, Sep 30 2019
%Y A327592 Cf. A000040.
%K A327592 nonn
%O A327592 1,1
%A A327592 _Philip Mizzi_, Sep 18 2019