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 A161912 #15 Jul 25 2024 04:42:47 %S A161912 0,0,0,0,1,1,1,1,1,4,2,6,4,4,4,6,7,7,7,9,5,7,7,11,11,12,10,10,6,8,14, %T A161912 16,16,14,20,18,15,19,19,21,19,19,21,21,19,15,23,33,27,26,24,26,22,30, %U A161912 28,30,28,26,28,30,20,28,38,36,31,31,37,41,45,43,39,43,39,43,45,43,43,47,43,49,49 %N A161912 a(n) = A040976(n+1) - A006218(n). %p A161912 A006218 := proc(n) add(floor(n/k),k=1..n) ; end: %p A161912 A040976 := proc(n) ithprime(n)-2 ; end: %p A161912 A161912 := proc(n) A040976(n+1)-A006218(n) ;end: %p A161912 seq(A161912(n),n=0..120) ; # _R. J. Mathar_, Jul 01 2009 %o A161912 (PARI) first(n)=my(v=primes(n+1),s); v[1]-=s=2; forfactored(k=1,n, v[k[1]+1]-=s+=numdiv(k)); v \\ _Charles R Greathouse IV_, Nov 03 2021 %Y A161912 Cf. A000005, A001223, A006218, A040976, A161911. %K A161912 easy,nonn,less %O A161912 0,10 %A A161912 _Omar E. Pol_, Jun 28 2009 %E A161912 Invalid formula deleted and sequence extended by _R. J. Mathar_, Jul 01 2009