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

1,2

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

Table of n, a(n) for n=1..15.

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

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

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 *)

Crossrefs

Cf. A120689.

Sequence in context: A336629 A303790 A327678 * A295815 A146498 A003750

Adjacent sequences: A130211 A130212 A130213 * A130215 A130216 A130217

Keyword

nonn,easy

Author

Artur Jasinski, Aug 04 2007

Extensions

More terms from Colin Barker, Sep 02 2013

Status

approved