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.
An n-tuply lonely non-twin prime is a non-twin prime that is sandwiched between exactly n pairs of prime twins on both sides. a(2)=1039 because 1039 is the first non-twin to be sandwiched between exactly 2 pairs of twins on each side (1019,1021,1031,1033 and 1049,1051,1061,1063).
istwp := proc(n)
if isprime(n) then
if isprime(n+2) or isprime(n-2) then
true;
else
false;
end if;
else
false;
end if;
end proc:
for i from 4 do
p := ithprime(i) ;
p1 := prevprime(p) ;
if istwp(p1) then
p2 := prevprime(p1) ;
if istwp(p2) then
p3 := prevprime(p2) ;
if istwp(p3) then
p1 := nextprime(p) ;
if istwp(p1) then
p2 := nextprime(p1) ;
if istwp(p2) then
p3 := nextprime(p2) ;
if istwp(p3) then
printf("%d\n",p) ;
end if;
end if;
end if;
end if;
end if;
end if;
end do: # R. J. Mathar, Jul 13 2013
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