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.
k=17; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((17^n-5^n)/12) \\ Charles R Greathouse IV, Feb 17 2017
k=18; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((18^n-5^n)/13) \\ Charles R Greathouse IV, Feb 17 2017
k=19; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((19^n-5^n)/14) \\ Charles R Greathouse IV, Feb 17 2017
k=13; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((13^n-5^n)/8) \\ Charles R Greathouse IV, Feb 17 2017
k=14; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,200}]
is(n)=isprime((14^n-5^n)/9) \\ Charles R Greathouse IV, Feb 17 2017
k=16; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((16^n-5^n)/11) \\ Charles R Greathouse IV, Feb 17 2017
k=8; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((8^n+5^n)/13) \\ Charles R Greathouse IV, Feb 17 2017
k=14; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n,1,100}]
is(n)=isprime((14^n+5^n)/19) \\ Charles R Greathouse IV, Feb 17 2017
Read by rows: m\n 1 2 3 4 5 6 7 8 9 10 11 2 3 3 3 3 4 0 0 3 5 3 5 13 3 6 3 0 0 0 5 7 5 3 3 5 3 3 8 3 0 3 0 19 0 7 9 0 3 0 0 3 0 3 7 10 19 0 3 0 0 0 31 0 3 11 17 5 3 3 5 3 5 7 5 3 12 3 0 0 0 3 0 3 0 0 0 3 etc.
t1[n_] := Floor[3/2 + Sqrt[2*n]]
m[n_] := Floor[(-1 + Sqrt[8*n-7])/2]
t2[n_] := n-m[n]*(m[n]+1)/2
b[n_] := GCD @@ Last /@ FactorInteger[n]
is[m_, n_] := GCD[m, n] == 1 && GCD[b[m], b[n]] == 1
Do[k=2, If[is[t1[n], t2[n]], While[ !PrimeQ[t1[n]^Prime[k] - t2[n]^Prime[k]], k++]; Print[Prime[k]], Print[0]], {n, 1, 663}] (* Eric Chen, Jun 01 2015 *)
a052409(n) = my(k=ispower(n)); if(k, k, n>1);
a(m, n) = {if (gcd(m,n) != 1, return (0)); if (gcd(a052409(m), a052409(n)) != 1, return (0)); forprime(p=3,, if (isprime((m^p-n^p)/(m-n)), return (p)););}
tabl(nn) = {for (m=2, nn, for(n=1, m-1, print1(a(m,n), ", ");); print(););} \\ Michel Marcus, Nov 19 2014
t1(n)=floor(3/2+sqrt(2*n)) t2(n)=n-binomial(floor(1/2+sqrt(2*n)), 2) b(n)=my(k=ispower(n)); if(k, k, n>1) a(n)=if(gcd(t1(n),t2(n)) !=1 || gcd(b(t1(n)), b(t2(n))) !=1, 0, forprime(p=3,2^24,if(ispseudoprime((t1(n)^p-t2(n)^p)/(t1(n)-t2(n))), return(p)))) \\ Eric Chen, Jun 01 2015
Select[Range[1, 10000], PrimeQ[(9^# - 7^#)/2] &]
for(n=1,10000, if(isprime((9^n - 7^n)/2), print1(n,", ")))
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