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 A060019 #13 Jun 06 2025 14:47:08 %S A060019 0,2,3,4,6,6,7,8,9,10,10,11,12,12,13,14,15,15,16,16,16,17,18,18,19,19, %T A060019 20,20,20,21,22,22,23,23,24,24,24,25,25,26,26,26,27,27,27,28,28,29,30, %U A060019 30,30,30,30,31,31,32,32,32,33,33,33,34,34,35,35,35 %N A060019 a(n) = floor(2*sqrt(prime(n)-2)) where prime(n) = n-th prime. %H A060019 J. R. Griggs, <a href="http://dx.doi.org/10.1016/S0012-365X(00)00203-X">Spanning subset sums for finite Abelian groups</a>, Discrete Math., 229 (2001), 89-99. %F A060019 For n=1, prime(1) is 2, and a(n) = 0. %o A060019 (PARI) a(n) = floor(2*sqrt(prime(n)-2)); \\ _Michel Marcus_, Nov 26 2015 %o A060019 (PARI) a(n,p=prime(n))=sqrtint(4*p-8) \\ _Charles R Greathouse IV_, Jan 24 2018 %o A060019 (Python) %o A060019 from math import isqrt %o A060019 from sympy import prime %o A060019 def A060019(n): return isqrt(prime(n)-2<<2) # _Chai Wah Wu_, Jun 06 2025 %Y A060019 Cf. A060018. %K A060019 nonn %O A060019 1,2 %A A060019 _N. J. A. Sloane_, Mar 17 2001 %E A060019 Offset set to 1 by _Michel Marcus_, Nov 26 2015