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 A378123 #8 Nov 20 2024 09:51:03 %S A378123 1,1,2,2,2,2,2,2,1,2,3,2,2,2,1,3,1,2,2,3,2,2,1,2,2,2,1,2,2,2,1,3,2,3, %T A378123 2,2,3,3,2,3,3,3,2,4,2,2,2,3,4,3,2,3,1,3,1,3,2,3,2,5,1,5,2,4,1,3,2,3, %U A378123 3,3,1,3,2,3,1,3,2,3,2,4,3,3,2,2,2,4 %N A378123 a(n) = number of prime divisors of the sum of the first n odd primes. %F A378123 a(n) = A001221(A071148(n)). %e A378123 3+5+7+11+13 = 39 = 3*13, so a(5) = 2. %t A378123 a[n_] := PrimeNu[Total[Prime[1+Range[n]]]]; Array[a, 500] %o A378123 (PARI) a378123(n)=omega(sum(k=2,n+1,prime(k))) \\ _Hugo Pfoertner_, Nov 19 2024 %Y A378123 Cf. A000040, A071215, A008334, A008335, A378122. %Y A378123 Cf. A001221, A071148. %K A378123 nonn %O A378123 1,3 %A A378123 _Clark Kimberling_, Nov 17 2024