A130214 Order of modular group of degree 5^(n-1)+1.

0, 60, 7800, 976500, 122070000, 15258787500, 1907348625000, 238418579062500, 29802322387500000, 3725290298460937500, 465661287307734375000, 58207660913467382812500, 7275957614183425781250000, 909494701772928237304687500, 113686837721616029736328125000

Offset: 1

Author

Artur Jasinski, Aug 04 2007

Keywords

• nonn
• easy

References

• E. Mathieu, Mémoire sur le nombre de valeurs que peut acquérir une fonction quand on y permute ses variables de toutes les manières possibles, Journ. de math. (2) 5 (1860), 9-42 (see p. 39).

Links

• Index entries for linear recurrences with constant coefficients, signature (130,-625).

Crossrefs

Cf. A120689.

Programs

Mathematica

Table[5^(x - 1) (5^(2 x - 2) - 1)/2, {x, 1, 15}]
LinearRecurrence[{130,-625},{0,60},30] (* Harvey P. Dale, Aug 09 2023 *)

Formula

a(n) = 5^(n - 1) (5^(2 n - 2) - 1)/2.

a(n) = 130*a(n-1)-625*a(n-2). G.f.: 60*x^2 / ((5*x-1)*(125*x-1)). - Colin Barker, Sep 02 2013

Extensions

More terms from Colin Barker, Sep 02 2013