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 A220850 #8 Dec 23 2012 23:44:06 %S A220850 1,2,4,6,8,10,14,17,22,28,35,43,53,65,78,93,111,129,153,179,210,245, %T A220850 285,328,381,441,508,582,668,764,870,990,1123,1270,1436,1625,1825, %U A220850 2054,2309,2590,2904,3246,3631,4052,4512,5022,5582,6197,6872,7612,8421,9312 %N A220850 a(n+1) is equal to a(n) plus the number of primes between a(n) and 2*a(n) inclusively. %H A220850 Robert G. Wilson v, <a href="/A220850/b220850.txt">Table of n, a(n) for n = 1..558</a> %e A220850 a(6) = the number of primes between a(5) and 2*a(5) plus a(5) = the number of primes [8, 16] + 8 = 2 + 8 = 10. %t A220850 f[n_] := PrimePi[ 2n] - PrimePi[n - 1]; NestList[# +f@# &, 1, 50] %Y A220850 Cf. A035250, A220851, inspired by A084140. %K A220850 easy,nonn %O A220850 1,2 %A A220850 _Robert G. Wilson v_, Dec 22 2012