A088612 - OEIS

%I #11 Aug 13 2024 01:56:02

%S 1,8,9,5,16,18,20,11,13,27,28,17,36,40,44,23,48,29,50,31,54,56,60,37,

%T 38,68,41,42,76,80,81,51,88,90,92,58,98,99,100,65,108,112,116,70,71,

%U 121,124,77,78,79,132,83,136,86,144,89,148,150,152,95,156,160,102,103,168

%N a(1) = 1, a(n) = n-th squarefree number if n is not squarefree else a(n) is the n-th nonsquarefree number.

%e a(9) = 13, the 9th squarefree number, A005117(9).

%o (Python)

%o # uses programs from A005117 and A013929

%o from sympy import factorint

%o def A088612(n): return A013929(n) if max(factorint(n).values(),default=0)<2 and n>1 else A005117(n) # _Chai Wah Wu_, Aug 12 2024

%Y Cf. A005117, A013929, A088611.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Oct 16 2003

%E Corrected and extended by _Ray Chandler_, Oct 18 2003