A024080 a(n) = 7^n - n^5.

1, 6, 17, 100, 1377, 13682, 109873, 806736, 5732033, 40294558, 282375249, 1977165692, 13841038369, 96888639114, 678222535025, 4747560750568, 33232929521025, 232630512567350, 1628413596020881, 11398895182897044

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..500

Programs

Magma

[7^n-n^5: n in [0..25]]; // Vincenzo Librandi, Jul 03 2011

Formula

From Chai Wah Wu, Jul 10 2016: (Start)

a(n) = 13*a(n-1) - 57*a(n-2) + 125*a(n-3) - 155*a(n-4) + 111*a(n-5) - 43*a(n-6) + 7*a(n-7) for n > 6.

G.f.: (-8*x^6 - 175*x^5 - 451*x^4 - 96*x^3 + 4*x^2 + 7*x - 1)/((x - 1)^6*(7*x - 1)). (End)