A115160 - OEIS

%I #7 May 13 2013 01:48:37

%S 33,63,75,125,365,489,492,684,693,723,954,1043,1185,1505,1623,1629,

%T 1736,1775,1899,1904,1925,2015,2051,2679,2883,3534,3774,3936,4332,

%U 4461,4739,4923,5445,5721,5847,6285,6348,6474,6783,7034,7478,8604,9576,9686,9863

%N Numbers that are not the sum of two triangular numbers and a fourth power.

%C There are 88 such numbers up to 2*10^9, the last one in this range being 1945428.

%H David W. Wilson, <a href="/A115160/b115160.txt">Table of n, a(n) for n = 1..88</a>

%o (PARI) sumset_lim(a,b,lim)=my(v=[],u,t);if(a==b,for(i=1,#a,u=List();for(j=i,#b,t=a[i]+b[j];if(t>lim,break);listput(u,t));v=vecsort(concat(v,Vec(u)),,8)),for(i=1,#a,u=List();for(j=1,#b,t=a[i]+b[j];if(t>lim,break);listput(u,t));v=vecsort(concat(v,Vec(u)),,8)));v

%o makev(lim)=my(n=floor(sqrt(2*lim)-1/2),v);sumset_lim(v=vector(n,k,k*(k-1)/2),v,lim)

%o is(n)=for(i=1,#v,if(ispower(n-v[i],4),return(0));if(v[i]>n,return(1)))

%o v=makev(1e5);

%o for(n=1,1e5,if(is(n),print1(n", "))) \\ _Charles R Greathouse IV_, Aug 17 2011

%Y Cf. A022552, A014158, A115159, A115161, A115162, A115163.

%K nonn

%O 1,1

%A _Giovanni Resta_, Jan 15 2006