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) = 700 because reverse concatenation of squares of 1 to 700 gives 490000488601......2516941 which is a 3742-digit prime number.
A000578(3) = 27. The only odd number less than 3 is 1 with A000578(1) = 1. Concatenating the two resulting cubes in descending order one gets 271 which is prime, so 3 is a term of the sequence.
fQ[n_] := PrimeQ[ FromDigits[ Flatten[ IntegerDigits[ Range[2n - 1, 1, -2]^3]]]]; k = 1; lst = {}; While[k < 1501, If[ fQ[k], AppendTo[lst, 2k - 1]; Print[2k - 1]]; k++]; lst (* Robert G. Wilson v, Sep 16 2015 *)
odd(n) = 2*n-1 con(n) = s=""; k=n; while(k > 0, s=Str(s, Str(odd(k)^3)); k--); eval(s) isok(n) = ispseudoprime(con(n)) terms(n) = i=0; x=1; while(i < n, if(isok(x), print1(odd(x), ", "); i++); x++) terms(4) \\ print initial four terms
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