%I #19 Nov 17 2022 05:26:54
%S 1,1,5,1,5,5,25,1,5,5,25,5,25,25,125,1,5,5,25,5,25,25,125,5,25,25,125,
%T 25,125,125,625,1,5,5,25,5,25,25,125,5,25,25,125,25,125,125,625,5,25,
%U 25,125,25,125,125,625,25,125,125,625,125,625,625,3125,1,5,5,25,5,25,25,125,5
%N a(n) = 5^(wt(n) - 1) where wt(n) = A000120(n).
%e From _Omar E. Pol_, Jul 21 2009: (Start)
%e If written as a triangle:
%e 1;
%e 1,5;
%e 1,5,5,25;
%e 1,5,5,25,5,25,25,125;
%e 1,5,5,25,5,25,25,125,5,25,25,125,25,125,125,625;
%e 1,5,5,25,5,25,25,125,5,25,25,125,25,125,125,625,5,25,25,125,25,125,125,625,...
%e (End)
%o (Python 3.10+)
%o def A151780(n): return 5**(n.bit_count()-1) # _Chai Wah Wu_, Nov 15 2022
%o (PARI) a(n) = 5^(hammingweight(n)-1); \\ _Michel Marcus_, Nov 15 2022
%Y Essentially A151779/6.
%Y Cf. A000120, A048881, A048896, A147610, A151783.
%Y Cf. A000351. - _Omar E. Pol_, Jul 21 2009
%K nonn
%O 1,3
%A _N. J. A. Sloane_, Jun 25 2009