A069477 a(n) = 60*n^2 + 180*n + 150.

390, 750, 1230, 1830, 2550, 3390, 4350, 5430, 6630, 7950, 9390, 10950, 12630, 14430, 16350, 18390, 20550, 22830, 25230, 27750, 30390, 33150, 36030, 39030, 42150, 45390, 48750, 52230, 55830, 59550, 63390, 67350, 71430, 75630, 79950, 84390, 88950, 93630, 98430

Offset

1,1

Comments

First differences of A068236, successive differences of (n+1)^5 - n^5 (A022521).

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); a(1)=390, a(2)=750, a(3)=1230. - Harvey P. Dale, Apr 06 2012

Sum_{n>=1} 1/a(n) = (Pi/60)*tanh(Pi/2) - 1/25. - Amiram Eldar, Jan 27 2022

Mathematica

Table[30 (2 n^2 + 6 n + 5), {n, 1, 100}] (* Vladimir Joseph Stephan Orlovsky, Jun 19 2011 *)
LinearRecurrence[{3, -3, 1}, {390, 750, 1230}, 40] (* Harvey P. Dale, Apr 06 2012 *)

Prog

(Magma) [30*(2*n^2 + 6*n + 5): n in [1..40]]; // Vincenzo Librandi, Nov 23 2011
(PARI) a(n)=60*n^2+180*n+150 \\ Charles R Greathouse IV, Nov 23 2011

Crossrefs

Cf. A101096, A022521, A068236, A069477.

Sequence in context: A228580 A242182 A136153 * A325993 A108573 A206653

Adjacent sequences: A069474 A069475 A069476 * A069478 A069479 A069480

Keyword

nonn,easy

Author

Eli McGowan (ejmcgowa(AT)mail.lakeheadu.ca), Apr 11 2002

Status

approved