A248918 - OEIS

%I #5 Oct 20 2014 14:44:35

%S 1,2,3,4,5,7,6,8,9,31,10,11,12,27,28,14,16,63,17,18,19,20,32,21,22,23,

%T 127,24,25,26,29,115,30,33,34,35,36,37,38,39,40,111,41,255,42,43,44,

%U 45,46,47,48,49,50,51,52,53,54,56,58,59,60,61,62,64,66,67

%N a(n) = index of (n+1)-th prime power in A247665.

%o (Haskell)

%o import Data.List (elemIndex); import Data.Maybe (fromJust)

%o a248918 = (+ 1) . fromJust . (`elemIndex` a247665_list) . a000961 . (+ 1)

%Y Cf. A248387 (subsequence), A000961.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Oct 16 2014