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.
%I A070155 #37 Apr 15 2024 03:29:31
%S A070155 4,6,150,180,240,270,420,570,1290,1320,2310,2550,2730,3360,3390,4260,
%T A070155 4650,5850,5880,6360,6780,9000,9240,9630,10530,10890,11970,13680,
%U A070155 13830,14010,14550,16230,16650,18060,18120,18540,19140,19380,21600,21840
%N A070155 Numbers k such that k-1, k+1 and k^2+1 are prime numbers.
%C A070155 Essentially the same as A129293. - _R. J. Mathar_, Jun 14 2008
%C A070155 Solutions to the equation: A000005(n^4-1) = 8. - _Enrique Pérez Herrero_, May 03 2012
%C A070155 Terms > 6 are multiples of 30. Subsequence of A070689. - _Zak Seidov_, Nov 12 2012
%C A070155 {a(n)-1} is a subsequence of A157468; for n>1, {a(n)^2+2} is a subsequence of A242720. - _Vladimir Shevelev_, Aug 31 2014
%H A070155 Amiram Eldar, <a href="/A070155/b070155.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%F A070155 For n>1, a(n)^2 = A242720(pi(a(n)-2)) - 2, where pi(n) is the prime counting function (A000720). - _Vladimir Shevelev_, Sep 02 2014
%e A070155 150 is a term since 149, 151 and 22501 are all primes.
%p A070155 select(n -> isprime(n-1) and isprime(n+1) and isprime(n^2+1), [seq(2*i,i=1..10000)]); # _Robert Israel_, Sep 02 2014
%t A070155 Do[s=n; If[PrimeQ[s-1]&&PrimeQ[s+1]&&PrimeQ[1+s^2], Print[n]], {n, 1, 1000000}]
%t A070155 Select[Range[22000],AllTrue[{#+1,#-1,#^2+1},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Dec 19 2014 *)
%o A070155 (PARI) is(k) = isprime(k-1) && isprime(k+1) && isprime(k^2+1); \\ _Amiram Eldar_, Apr 15 2024
%Y A070155 Cf. A000005, A000720, A001359, A006512, A014574, A002496, A005574, A070156, A070689, A129293, A157468, A242720.
%K A070155 easy,nonn
%O A070155 1,1
%A A070155 _Labos Elemer_, Apr 23 2002