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 A078139 #15 Apr 05 2025 06:32:57 %S A078139 2,3,5,7,11,19,23 %N A078139 Primes which cannot be written as sum of squares>1. %C A078139 From _Hieronymus Fischer_, Nov 11 2007: (Start) %C A078139 Equivalently, prime numbers which cannot be written as sum of squares of primes (see A078137 for the proof). %C A078139 Equivalently, prime numbers which cannot be written as sum of squares of 2 and 3 (see A078137 for the proof). %C A078139 The sequence is finite, since numbers > 23 can be written as sums of squares >1 (see A078135). %C A078139 Explicit representation as sum of squares of primes, or rather of squares of 2 and 3, for numbers m>23: we have m=c*2^2+d*3^2, where c:=(floor(m/4) - 2*(m mod 4))>=0, d:=m mod 4. For that, the finiteness of the sequence is proved. (End) %H A078139 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SquareNumber.html">Square Number</a>. %H A078139 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a> %Y A078139 Cf. A000290, A078134, A078138, A000040, A078133. %Y A078139 Cf. A078135, A090677, A078137, A134754, A134755. %K A078139 nonn,fini,full %O A078139 1,1 %A A078139 _Reinhard Zumkeller_, Nov 19 2002