|
%I #9 Apr 13 2020 10:15:23
%S 2,140,102424,43322844421220
%N a(n) is the least integer that is the sum of two nonzero tetrahedral numbers in exactly n ways.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TetrahedralNumber.html">Tetrahedral Number</a>
%H <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a>
%e Let Te(k) denote the k-th tetrahedral number, then
%e a(1) = Te(1) + Te(1);
%e a(2) = Te(7) + Te(6) = Te(8) + Te(4);
%e a(3) = Te(82) + Te(34) = Te(83) + Te(27) = Te(84) + Te(7);
%e a(4) = Te(60500) + Te(33760) = Te(53311) + Te(47682) = Te(63383) + Te(17423) = Te(63495) + Te(15790);
%Y Cf. A000292, A010329, A011541, A053587.
%K nonn,hard,more
%O 1,1
%A _Ilya Gutkovskiy_, Apr 12 2020
%E a(4) from _Giovanni Resta_, Apr 13 2020
| 