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.

A154772 Numbers m such that 180 m^2 is the average of a twin prime pair.

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%I A154772 #10 Dec 25 2019 04:49:47
%S A154772 1,3,7,14,22,29,41,46,62,64,67,88,167,179,207,231,239,249,263,266,286,
%T A154772 290,309,315,322,323,326,344,350,353,354,372,392,421,444,454,458,496,
%U A154772 505,553,560,561,571,585,613,636,647,661,669,682,745,788,790,791,815
%N A154772 Numbers m such that 180 m^2 is the average of a twin prime pair.
%C A154772 Inspired by Z. Seidov's post to the SeqFan list, cf. link. This yields A154672 as 180 a(n)^2. Indeed, if N is such that N/5 is a square, then M=5m^2 and this can't by the average of a twin prime pair unless m=6a.
%H A154772 Amiram Eldar, <a href="/A154772/b154772.txt">Table of n, a(n) for n = 1..10000</a>
%H A154772 Zak Seidov, <a href="http://zak08.livejournal.com/4070.html">"A154676"</a>, Jan 15 2009
%F A154772 a(n) = sqrt(A154672(n)/180)
%t A154772 Select[Range[10^3], And @@ PrimeQ[180#^2 + {-1, 1}] &] (* _Amiram Eldar_, Dec 25 2019 *)
%o A154772 (PARI) for(i=1,999, isprime(180*i^2+1) & isprime(180*i^2-1) & print1(i","))
%Y A154772 Cf. A014574, A037073, A154331, A154672.
%K A154772 nonn
%O A154772 1,2
%A A154772 _M. F. Hasler_, Jan 15 2009