A268583 - OEIS

%I #12 Feb 07 2016 20:07:04

%S 7859,681179092750,4466203788801326865111

%N Happycab numbers: the smallest happy number that is the sum of two cubes of happy numbers in n different ways.

%C a(n)>3.6*10^24 for n >=4. This lower bound was established by exhaustive crowd computing.

%C Upper bounds:

%C a(4)<= 3915335521240189321820073984

%C =467175960^3+1562319144^3

%C =569783808^3+1550898288^3

%C =1085420968^3+1381483928^3

%C =1157553216^3+1332193392^3

%C a(5)<=

%C 1508202165690304620654479410485250200981504

%C =12156471201588^3+114634141265868^3

%C =33798481396036^3+113692639229372^3

%C =64341822928208^3+107486686558048^3

%C =69397851840576^3+105492106344912^3

%C =72561474196232^3+104039736026296^3

%e a(1) = 7859 = 10^3+19^3;

%e a(2) = 681179092750 = 4365^3+8425^3 = 5275^3+8115^3;

%e a(3) = 4466203788801326865111 = 6193863^3+16170804^3 = 8456292^3+15688647^3 = 9457695^3+15354846^3.

%Y Cf. A011541, A007770.

%K nonn,hard,more,bref

%O 1,1

%A _Corinna Regina Böger_, Feb 07 2016