A093461 a(1)=1, a(n) = 2*(n^(n-1)-1)/(n-1) for n >= 2.

1, 2, 8, 42, 312, 3110, 39216, 599186, 10761680, 222222222, 5187484920, 135092431034, 3883014187080, 122109965116022, 4170418003627232, 153722867280912930, 6082648984458358560, 257166065851611356702

Offset

1,2

Comments

Proposition: n^(n-1) - 1 == 0 (mod (n-1)^2). Hence a(n) == 0 mod (n-1).

a(n) is the common difference of the arithmetic progression in row n of A111568. Written in base n, a(n) has n-1 digits equal to 2 (for example, a(10)=222222222). - Emeric Deutsch, Aug 08 2005

Links

Table of n, a(n) for n=1..18.

Formula

a(1) = 1, a(n) = 2*(n^(n-1) - 1)/(n-1) for n > 1.

Maple

a:=proc(n) if n=1 then 1 else 2*(n^(n-1)-1)/(n-1) fi end: seq(a(n), n=1..20); # Emeric Deutsch, Aug 08 2005

Mathematica

f[n_] := (2*n^(n-1) - 2)/(n-1); Table[f[i], {i, 2, 30}] (* Ryan Propper, Aug 08 2005 *)

Crossrefs

Cf. A093460, A093462.

Cf. A111568.

Sequence in context: A352646 A320343 A002856 * A191994 A153524 A153552

Adjacent sequences: A093458 A093459 A093460 * A093462 A093463 A093464

Keyword

nonn

Author

Amarnath Murthy, Apr 05 2004

Extensions

More terms from Emeric Deutsch and Ryan Propper, Aug 08 2005

Status

approved