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.
a(4) = 78 because 353 = prime(prime(20)), 431 = prime(prime(23)), 509 = prime(prime(25)), 587 = prime(prime(28)), and 431-353 = 509-431 = 587-509 = 78. For the corresponding arithmetic progressions, see _Charles R Greathouse IV_'s example in A278735. - _Bobby Jacobs_, Jan 02 2017
a(4) = 587 because 353 = prime(prime(20)), 431 = prime(prime(23)), 509 = prime(prime(25)), 587 = prime(prime(28)), and 431-353 = 509-431 = 587-509 = 78. From _Charles R Greathouse IV_, Nov 27 2016: (Start) The corresponding arithmetic progressions are 3; 3, 5; 5, 11, 17; 353, 431, 509, 587; 13297, 21937, 30577, 39217, 47857; 1561423, 2716423, 3871423, 5026423, 6181423, 7336423; and with the main diagonal being terms of this sequence. (End)
findAP(len)=my(t); if(len<3, return(v[len])); for(i=len, #v, for(j=1, i-len+1, t=(v[i]-v[j])/(len-1); if(denominator(t)>1, next); forstep(k=v[j]+t, v[i]-t, t, if(!setsearch(v, k), next(2))); return(vector(len, k, v[j]+(k-1)*t)))); "not found" listPIP(lim)=my(v=List(), p); forprime(q=2, lim, if(isprime(p++), listput(v, q))); Vec(v) v=listPIP(1e7); apply(findAP, [1..6]) \\ Charles R Greathouse IV, Nov 27 2016
a(4) = 353 because 353 = prime(prime(20)), 431 = prime(prime(23)), 509 = prime(prime(25)), 587 = prime(prime(28)), and 431-353 = 509-431 = 587-509 = 78. The corresponding arithmetic progressions are 3; 3, 5; 5, 11, 17; 353, 431, 509, 587; 13297, 21937, 30577, 39217, 47857; 1561423, 2716423, 3871423, 5026423, 6181423, 7336423; ...
Comments