A226795 - OEIS

%I #5 Feb 18 2021 21:28:12

%S 1,4,5,8,25,29,41,44,65,172,176,212,365,368,389,536,1201,1205,1241,

%T 1565,3281,3284,3305,3452,4481,8404,8408,8444,8768,11684,29525,29528,

%U 29549,29696,30725,37928,58825,58829,58865,59189,62105,88349,265721

%N Numbers of the form (7^j + 9^k)/2, for j and k >= 0.

%t a = 7; b = 9; mx = 600000; Union[Flatten[Table[a^n + b^m, {m, 0, Log[b, mx]}, {n, 0, Log[a, mx - b^m]}]]]/2

%o (PARI) list(lim)=my(v=List(),J,K); lim=(lim\1)*2; for(j=0,logint(lim-1,7), J=7^j; K=1; while(J+K<=lim, listput(v,(J+K)/2); K*=9)); Set(v) \\ _Charles R Greathouse IV_, Feb 18 2021

%Y Cf. A226831 (7^j + 9^k).

%K nonn,easy

%O 1,2

%A _T. D. Noe_, Jun 19 2013