A083474 a(n) = T(n)^2-n!, where T(n) is the n-th triangular number.

0, 7, 30, 76, 105, -279, -4256, -39024, -360855, -3625775, -39912444, -478995516, -6227012519, -87178280175, -1307674353600, -20922789869504, -355687428072591, -6402373705698759, -121645100408795900, -2432902008176595900, -51090942171709386639

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Example

a(3) = T(3)^2-3! = 6^2-6 = 36-6 = 30.

Mathematica

Table[((n(n+1))/2)^2-n!, {n, 30}] (* Harvey P. Dale, Nov 23 2011 *)

Prog

(PARI) t(n)=n*(n+1)/2
for(i=1, 50, print1(t(i)^2-i!", "))

Crossrefs

Cf. A000142, A000217, A000537.

Sequence in context: A116283 A139274 A086640 * A030440 A256225 A339196

Adjacent sequences: A083471 A083472 A083473 * A083475 A083476 A083477

Keyword

sign,easy,less

Author

Jon Perry, Jun 08 2003

Extensions

Corrected by Harvey P. Dale, Nov 23 2011

Status

approved