A099185 Iterated octahedral numbers, starting at a(0) = 2.

2, 6, 146, 2074806, 5954444157018557346, 140744820294208035204656447906095566299588102457814757606

Offset: 0

Author

Jonathan Vos Post, Nov 15 2004

Keywords

• easy
• nonn
• less

Comments

For additional terms see b-file.

References

• Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, p. 50, 1996.
• Dickson, L. E. History of the Theory of Numbers, Vol. 2: Diophantine Analysis. New York: Chelsea, 1952.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..7
• Eric Weisstein's World of Mathematics, Octahedral Number.

Crossrefs

Cf. A007501, A005900.

Programs

Mathematica

RecurrenceTable[{a[0]==2, a[n+1]==(2 a[n]^3 + a[n])/3}, a, {n, 6}] (* Vincenzo Librandi, Sep 16 2018 *)

Formula

a(0) = 2, a(n+1) = oct(a(n)) = (2*a(n)^3 + a(n))/3.

Extensions

Edited by Jianing Song, Sep 16 2018