A122471 a(n)=7*a(n-1)-n for n> 0, a(0)=1.

1, 6, 40, 277, 1935, 13540, 94774, 663411, 4643869, 32507074, 227549508, 1592846545, 11149925803, 78049480608, 546346364242, 3824424549679, 26770971847737, 187396802934142, 1311777620538976, 9182443343772813

Offset

0,2

Comments

From a quiz.

References

K. Russell and P. Carter, Number Puzzles, W. Foulsham and Co. Ltd. (1993).

Links

Table of n, a(n) for n=0..19.

Index entries for linear recurrences with constant coefficients, signature (9, -15, 7).

Formula

G.f.: -(((x-3)*x+1)/((x-1)^2*(7*x-1))). - Harvey P. Dale, Jun 15 2011

a(0)=1, a(1)=6, a(2)=40, a(n)=9*a(n-1)-15*a(n-2)+7*a(n-3). - Harvey P. Dale, Jun 15 2011

Mathematica

RecurrenceTable[{a[0]==1, a[n]==7a[n-1]-n}, a[n], {n, 0, 20}] (* or *) LinearRecurrence[{9, -15, 7}, {1, 6, 40}, 31](* Harvey P. Dale, Jun 15 2011 *)

Prog

(PARI) a(n)=if(n>0, 7*a(n-1)-n, 1) for(n=0, 30, print1(a(n), ", "))

Crossrefs

Sequence in context: A123357 A081016 A083426 * A178397 A090041 A069720

Adjacent sequences: A122468 A122469 A122470 * A122472 A122473 A122474

Keyword

nonn

Author

Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 14 2006

Status

approved