OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
FORMULA
G.f.: x*(647*x^6+36942*x^5+195681*x^4+195716*x^3+36921*x^2+654*x-1)/(1-x)^7. - Alois P. Heinz, Jun 24 2021
a(n) = 648*(n-1)^6 - 1 = 648*A001014(n-1) - 1. - Hugo Pfoertner, Jun 24 2021
EXAMPLE
647 = 2*18^2 - 1 = 3*6^3 - 1. Thus, 647 is in this sequence.
MATHEMATICA
Intersection[Table[2 n^2 - 1, {n, 300000}], Table[3 n^3 - 1, {n, 100000}]]
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Tanya Khovanova, Jun 24 2021
STATUS
approved