A025477 - OEIS

%I #23 Oct 24 2023 04:41:04

%S 0,2,3,2,4,2,3,5,2,6,4,2,3,7,2,5,8,2,3,2,9,2,4,6,2,2,10,3,2,2,2,11,7,

%T 3,2,4,2,5,2,2,12,2,3,2,2,2,8,3,2,2,13,2,2,2,2,2,3,2,4,6,2,14,5,2,2,2,

%U 9,2,2,3,2,2,2,4,3,2,2,2,15,2,2,2,2,2,2,3,2,2,2,2,2,10,2,16,2,3,2,2,2,2,7,2,3,2

%N a(n) = exponent of the n-th nontrivial prime power A025475(n).

%H Michael De Vlieger, <a href="/A025477/b025477.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A051903(A025475(n)) = A001222(A025475(n)). - _Reinhard Zumkeller_, Mar 10 2003

%t With[{nn = 2^20}, {0}~Join~Map[FactorInteger[#][[1, -1]] &, Select[Union@ Flatten@ Table[a^2*b^3, {b, nn^(1/3)}, {a, Sqrt[nn/b^3]}], PrimePowerQ] ] ] (* _Michael De Vlieger_, Oct 23 2023 *)

%Y Cf. A001222, A025475, A051903.

%K easy,nonn

%O 1,2

%A _David W. Wilson_

%E Edited by _N. J. A. Sloane_, Jan 17 2009 at the suggestion of _R. J. Mathar_

%E Name edited by _Michael De Vlieger_, Oct 23 2023