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 A261543 #16 Feb 16 2025 08:33:26 %S A261543 2,5,8,15,20,42,60,137,210,520,828,2124,3418,8895,14370,37561,60747, %T A261543 158959,257169,673198,1089220,2851513,4613807,12078987,19544166, %U A261543 51167164,82790160,216747314,350704463,918156051,1485607642,3889371138,6293134627 %N A261543 Numbers of the form (prime(k) + Fibonacci(k))/2. %C A261543 The numbers represented as the arithmetic mean of the Fibonacci numbers and prime numbers with identical indices. %H A261543 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeNumber.html">Prime Number </a> %H A261543 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FibonacciNumber.html">Fibonacci Number </a> %F A261543 a(n) = (prime(A001651(n + 1)) + Fibonacci(A001651(n + 1)))/2 %e A261543 a(1) = (prime(2) + Fibonacci(2))/2 = (3 + 1)/2 = 2. %t A261543 Select[Array[(Prime[#] + Fibonacci@ #)/2 &, 50], IntegerQ] (* _Michael De Vlieger_, Aug 24 2015 *) %o A261543 (PARI) a(n)=n+=n\2+1; (prime(n)+fibonacci(n))/2 \\ _Charles R Greathouse IV_, Aug 24 2015 %Y A261543 Cf. A000040, A000045, A004397, A001651. %K A261543 nonn,easy %O A261543 1,1 %A A261543 _Ilya Gutkovskiy_, Aug 24 2015