A079610 a(n) = (5*n+1)*(5*n+3)*(5*n+5).

15, 480, 2145, 5760, 12075, 21840, 35805, 54720, 79335, 110400, 148665, 194880, 249795, 314160, 388725, 474240, 571455, 681120, 803985, 940800, 1092315, 1259280, 1442445, 1642560, 1860375, 2096640, 2352105, 2627520, 2923635, 3241200, 3580965, 3943680

Offset

0,1

References

R. Tijdeman, Some applications of Diophantine approximation, pp. 261-284 of Surveys in Number Theory (Urbana, May 21, 2000), ed. M. A. Bennett et al., Peters, 2003.

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

Formula

Sum_{n>=0} 1/a(n) is transcendental (cf. Tijdeman).

G.f.: 15*(1 + 28*x + 21*x^2)/(1-x)^4. - Colin Barker, Apr 28 2012

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). - Vincenzo Librandi, Jun 23 2012

Mathematica

Times@@@(#+{1, 3, 5}&/@(5*Range[0, 50])) (* Harvey P. Dale, Jan 01 2011 *)
LinearRecurrence[{4, -6, 4, -1}, {15, 480, 2145, 5760}, 40] (* Vincenzo Librandi, Jun 23 2012 *)

Prog

(Magma) I:=[15, 480, 2145, 5760]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Jun 23 2012

Crossrefs

Sequence in context: A129892 A275411 A289185 * A218803 A252929 A218198

Adjacent sequences: A079607 A079608 A079609 * A079611 A079612 A079613

Keyword

nonn,easy

Author

N. J. A. Sloane, Jan 28 2003

Status

approved