1,1

Table of n, a(n) for n=1..4.

Eric Weisstein's World of Mathematics, Tetrahedral Number

Index to sequences related to pyramidal numbers

Let Te(k) denote the k-th tetrahedral number, then

a(1) = Te(1) + Te(1);

a(2) = Te(7) + Te(6) = Te(8) + Te(4);

a(3) = Te(82) + Te(34) = Te(83) + Te(27) = Te(84) + Te(7);

a(4) = Te(60500) + Te(33760) = Te(53311) + Te(47682) = Te(63383) + Te(17423) = Te(63495) + Te(15790);

Cf. A000292, A010329, A011541, A053587.

Sequence in context: A220513 A120814 A221601 * A115890 A356747 A215187

Adjacent sequences: A334010 A334011 A334012 * A334014 A334015 A334016

nonn,hard,more

Ilya Gutkovskiy, Apr 12 2020

a(4) from Giovanni Resta, Apr 13 2020

approved